Optical head device and optical recording and reproducing apparatus

ABSTRACT

An optical head device and an optical recording and reproducing apparatus using this optical head device, which can record information and reproduce the recorded information at any of optical recording media, such as a next generation optical recording medium, in which the wavelength of the light source is made to be shorter, the numerical aperture of the objective lens is made to be higher, and the thickness of the recording medium is made to be thinner, and conventional recording media of DVD and CD standards, are provided. A light having wavelength of 405 nm, emitted from one of optics, is inputted to an objective lens as a collimated light, and is focused on a disk having thickness of 0.1 mm. A light having wavelength of 650 nm, emitted from the other of optics, is inputted to the objective lens as a diverged light, and is focused on a disk having thickness of 0.6 mm. A spherical aberration, which remains for the light having wavelength of 650 nm, is decreased by the change of the magnification of the objective lens, further the decreased spherical aberration is decreased by using a wavelength selective filter.

BACKGROUND OF THE INVENTION

The present invention relates to an optical head device and an opticalrecording and reproducing apparatus using this optical head device,which records information and reproduces the recorded information atplural types of optical recording media in which the thickness ofsubstrates of the optical recording media is different from one another.

DESCRIPTION OF THE RELATED ART

The recording density at the optical recording and reproducing apparatusis in inverse proportion to the second power of the diameter of afocused light spot formed on an optical recording medium by an opticalhead device. That is, the smaller the diameter of the focused light spotbecomes, the higher the recording density becomes. The diameter of thefocused light spot is in proportion to the wavelength of the lightsource at the optical head device, and is in inverse proportion to thenumerical aperture of the objective lens. Therefore, the shorter thewavelength of the light source is and the higher the numerical apertureof the objective lens is, the smaller the diameter of the focused lightspot becomes.

On the other hand, when the optical recording medium inclines for theobjective lens, the shape of the focused light spot is changed by thecoma aberration, and the recording and reproducing characteristicsdeteriorate. The coma aberration is in inverse proportion to thewavelength of the light source, and is in proportion to the third powerof the numerical aperture of the objective lens and the thickness of thesubstrate of the optical recording medium. Consequently, in case thatoptical recording media whose substrate thickness is the same are used,when the wavelength of the light source is short and the numericalaperture of the objective lens is high, the margin in the recording andreproducing characteristics for the incline of the optical recordingmedia becomes small.

Therefore, for making the recording density high, at an opticalrecording and reproducing apparatus, in which the wavelength of thelight source is short and the numerical aperture of the objective lensis high, in order to obtain a sufficient margin for the incline of theoptical recording medium, the thickness of the substrate of the opticalrecording medium is made to be thin.

At the standard of the compact disk (CD) whose capacity is 650 MB, thewavelength of the light source is 780 nm, the numerical aperture of theobjective lens is 0.45, and the thickness of the substrate is 1.2 mm.And at the standard of the digital versatile disk (DVD) whose capacityis 4.7 GB, the wavelength of the light source is 650 nm, the numericalaperture of the objective lens is 0.6, and the thickness of thesubstrate is 0.6 mm.

At a general use optical head device, its objective lens is designed sothat the spherical aberration is cancelled for a disk whose substratehas designated thickness. Therefore, when the optical head devicerecords and reproduces information for a disk whose substrate hasdifferent thickness, the spherical aberration remains, and normalrecording and reproducing cannot be executed. In order to solve thisproblem, an optical recording and reproducing apparatus, which has aninterchangeable function that can record and reproduce information atboth disks of the CD standard and the DVD standard, has been proposed.

As a first conventional optical head device, which can record andreproduce information at both disks of the CD standard and the DVDstandard, there is an optical head device, which has been disclosed inJapanese Patent Application Laid-Open No. HEI 10-334504. FIG. 1 is ablock diagram showing a structure of the optical head device at theJapanese Patent Application Laid-Open No. HEI 10-334504.

In FIG. 1, each of optics 1 f and 1 g provides a semiconductor laser anda photo detector that receives a light reflected from one of disks. Thewavelength of the semiconductor laser in the optics 1 f is 650 nm, andthe wavelength of the semiconductor laser in the optics 1 g is 780 nm.An interference filter 2 h transmits a light having wavelength of 650nm, and reflects a light having wavelength of 780 nm.

A light emitted from the semiconductor laser in the optics 1 f transmitsthe interference filter 2 h and a wavelength selective filter 3 c. Andthe transmitted light is inputted to an objective lens 4 b as acollimated light and is focused on a disk 15 b, whose thickness is 0.6mm, of the DVD standard. A light reflected from the disk 5 b transmitsthe objective lens 4 b, the wavelength selective filter 3 c, and theinterference filter 2 h in the inverse direction, and the photo detectorin the optics 1 f receives the transmitted light.

A light emitted from the semiconductor laser in the optics 1 g isreflected at the interference filter 2 h and transmits the wavelengthselective filter 3 c. And the transmitted light is inputted to theobjective lens 4 b as a collimated light and is focused on a disk 5 c,whose thickness is 1.2 mm, of the CD standard. A light reflected fromthe disk 5 c transmits the objective lens 4 b, the wavelength selectivefilter 3 c in the inverse direction, and is reflected at theinterference filter 2 h, and the photo detector in the optics 1 greceives the transmitted light. The objective lens 4 b has a sphericalaberration, which cancels a spherical aberration generated at the timewhen the light, whose wavelength is 650 nm, transmits through the disk 5b whose thickness is 0.6 mm.

FIG. 2 is a diagram showing the wavelength selective filter 3 c shown inFIG. 1. In FIG. 2 (a), the plane view of the wavelength selective filter3 c is shown, and in FIG. 2 (b), the sectional view of the wavelengthselective filter 3 c is shown. As shown in FIG. 2, the wavelengthselective filter 3 c is composed of a glass substrate 8 c, a phasefilter pattern 6 b having concentric circle shapes formed on the glasssubstrate 8 c, and a multi layered dielectric film 7 f formed on theglass substrate 8 c. When the effective diameter of the objective lens 4b, shown as a dotted line in FIG. 2 (a), is defined as 2 d, the phasefilter pattern 6 b is formed only within the circular region of thediameter 2 e, which is smaller than the diameter 2 d.

As shown in FIG. 2 (b), the cross-section of the phase filter pattern 6b has a four level step shape. The height of each step of the phasefilter pattern 6 b is set to be a value so that the phase difference oflight transmitting between a part with a pattern and a part without apattern at each step becomes 2π (equivalent to 0) for the wavelength 650nm. At this time, this phase difference becomes 1.67π (equivalent to−0.33π) for the wavelength 780 nm.

Therefore, the phase filter pattern 6 b does not change the phasedistribution for the light having wavelength of 650 nm, and changes thephase distribution for the light having wavelength of 780 nm. In casethat the wavelength selective filter 3 c is not used, when the lighthaving wavelength of 780 nm, inputted to the objective lens 4 b as acollimated light, was transmitted through the substrate having thicknessof 1.2 mm, a spherical aberration remains. However, the phase filterpattern 6 b is designed so that the change of the phase distribution forthe light having wavelength of 780 nm decreases the remaining sphericalaberration.

The multi layered dielectric film 7 f is formed at only the regionoutside the circle of the diameter 2 e. The multi layered dielectricfilm 7 f transmits all of the light having wavelength of 650 nm andreflects all of the light having wavelength of 780 nm. And also themulti layered dielectric film 7 f makes the phase difference of light,transmitting through between within the circle of the diameter 2 e andoutside the circle of the diameter 2 e for the light having wavelengthof 650 nm, adjust to be integer times the value of 2π. That is, at thewavelength selective filter 3 c, the light having wavelength of 650 nmis all transmitted, and the light having the wavelength of 780 nm is alltransmitted within the region of the circle of the diameter 2 e and isall reflected outside the region of the circle of the diameter 2 e.Therefore, when the focal distance of the objective lens 4 b is decidedas “fb”, the effective numerical aperture for the light havingwavelength of 650 nm is given as “d/fb”, and the effective numericalaperture for the bight having wavelength of 780 nm is given as “e/fb”.For example, it is set to be that the “d/fb”= 0.6, and the “e/fb”=0.45.

As a second conventional optical head device, which can record andreproduce information at both disks of the CD standard and the DVDstandard, there is an optical head device, which has been disclosed inJapanese Patent Application Laid-Open No. HEI 9-274730. FIG. 3 is ablock diagram showing a structure of the optical head device at theJapanese Patent Application Laid-Open No. HEI 9-274730.

In FIG. 3, each of modules 27 a and 27 b provides a semiconductor laserand a photo detector that receives a light reflected from one of disks.The wavelength of the semiconductor laser in the module 27 a is 650 nm,and the wavelength of the semiconductor laser in the module 27 b is 780nm. An interference filter 2 h transmits a light having wavelength of650 nm, and reflects a light having wavelength of 780 nm.

A light emitted from the semiconductor laser in the module 27 atransmits the interference filter 2 h, a collimator lens 10 d, and anaperture controlling element 21 c. And the transmitted light is inputtedto an objective lens 4 b as a collimated light and is focused on a disk5 b, whose thickness is 0.6 mm, of the DVD standard. A light reflectedfrom the disk 5 b transmits the objective lens 4 b, the aperturecontrolling element 21 c, the collimator lens 10 d, and the interferencefilter 2 h in the inverse direction, and the photo detector in themodule 27 a receives the transmitted light.

A light emitted from the semiconductor laser in the module 27 b isreflected at the interference filter 2 h, and the reflected light istransmitted through the collimator lens 10 d and the aperturecontrolling element 21 c. And the transmitted light is inputted to theobjective lens 4 b as a diverged light and is focused on a disk 5 c,whose thickness is 1.2 mm, of the CD standard. A light reflected fromthe disk 5 c transmits the objective lens 4 b, the aperture controllingelement 21 c, the collimator lens 10 d in the inverse direction, and isreflected at the interference filter 2 h, and the photo detector in themodule 27 b receives the transmitted light.

The objective lens 4 b has a spherical aberration, which cancels aspherical aberration generated at the time when the light, whosewavelength is 650 nm, transmits through the disk 5 b whose thickness is0.6 mm. A spherical aberration remains when the light whose wavelengthis 780 nm, inputted to the objective lens 4 b as a collimated light,transmits through the disk 5 c whose thickness is 1.2 mm. However, whena light, whose wavelength is 780 nm, is inputted to the objective lens 4b as a diverged light, a new aberration is generated by the change ofthe magnification of the objective lens 4 b, and this works to decreasethe remaining spherical aberration.

FIG. 4 is a diagram showing the aperture controlling element 21 c shownin FIG. 3. In FIG. 4 (a), the plane view of the aperture controllingelement 21 c is shown, and in FIG. 4 (b), the sectional view of theaperture controlling element 21 c is shown. As shown in FIG. 4, theaperture controlling element 21 c is composed of a glass substrate 8 c,and a phase compensation film 28 formed on the glass substrate 8 c and amulti layered dielectric film 7 g formed on the glass substrate 8 c.When the effective diameter of the objective lens 4 b, shown as a dottedline in FIG. 4 (a), is defined as 2 d, the multi layered dielectric film7 g is formed only at the region outside the diameter 2 e, which issmaller than the diameter 2 d. The multi layered dielectric film 7 gtransmits all the light having wavelength of 650 nm, and reflects allthe light having wavelength of 780 nm.

That is, at the aperture controlling element 21 c, the light havingwavelength of 650 nm is all transmitted, and the light having wavelengthof 780 nm is all transmitted within the region of the circle of thediameter 2 e and is all reflected outside the region of the circle ofthe diameter 2 e. Therefore, when the focal distance of the objectivelens 4 b is decided as “fb”, the effective numerical aperture for thelight having wavelength of 650 nm is given as “d/fb”, and the effectivenumerical aperture for the light having wavelength of 780 nm is given as“e/fb”. For example, it is set as the “d/fb”=0.6, and the “e/fb”=0.45.

The phase compensation film 28 is formed at only inside the circularregion of the diameter 2 e. The phase compensation film 28 works toadjust the phase difference of light, transmitting through between theinside, of the circular region of the diameter 2 e and the outside ofthat, to integer times the value of 2π.

Recently, in order to make the recording density much higher, a nextgeneration standard, in which the wavelength of the light source is madeto be shorter, the numerical aperture of the objective lens is made tobe higher, and the thickness of the substrate of the optical recordingmedium is made to be thinner, has been proposed. For example, inTechnical Digest, pp. 24-25, at International Symposium on OpticalMemory 2000, a next generation standard, in which the wavelength of thelight source is 405 nm, the numerical aperture of the objective lens is0.7, the thickness of the disk substrate is 0.12 mm, and the informationcapacity is 17 GB, has been proposed. In this case, an optical headdevice, which has an interchangeable function being able to record andreproduce information at all of the next generation standard and theconventional DVD and CD standards, is required.

As a first example, the wavelength selective filter 3 c at the firstconventional optical head device shown in FIG. 1 is studied. In thiscase, the interchangeability between a next generation standard, inwhich the wavelength of the light source is 405 nm, the numericalaperture of the objective lens is 0.7, and the thickness of the disksubstrate is 0.1 mm, and the conventional DVD standard is studied. Asemiconductor laser having wavelength of 405 nm is used to record andreproduce information for the disk having thickness of 0.1 mm of thenext generation standard. And a semiconductor laser having wavelength of650 nm is used to record and reproduce information for the disk havingthickness of 0.6 mm of the DVD standard. The objective lens 4 b has aspherical aberration, which cancels a spherical aberration generating atthe time when a light having wavelength of 405 nm, inputted to theobjective lens 4 b as a collimated light, transmits through thesubstrate having thickness of 0.1 mm.

The cross-section of the phase filter pattern 6 b in the wavelengthselective filter 3 c is a five level step shape. The height of each stepof the phase filter pattern 6 b is set to be a value so that the phasedifference of light transmitting between a part with a pattern and apart without a pattern at each step becomes 2π (equivalent to 0) for thewavelength 405 nm. At this time, this phase difference becomes 1.25%(equivalent to −0.75π) for the wavelength 650 nm.

Therefore, the phase filter pattern 6 b does not change the phasedistribution for the light having wavelength of 405 nm, and changes thephase distribution for the light having wavelength of 650 nm. In casethat the wavelength selective filter 3 c is not used, when the lighthaving wavelength of 650 nm, inputted to the objective lens 4 b as acollimated light, was transmitted through the substrate having thicknessof 0.6 mm, a spherical aberration remains. The phase filter pattern 6 bis designed so that the change of the phase distribution for the lighthaving wavelength of 650 nm decreases the remaining sphericalaberration.

FIG. 5 is a table showing the designed result of the phase filterpattern 6 b when the phase filter pattern 6 b of the first conventionaloptical head device was used at the interchangeability between the nextgeneration standard and the conventional DVD standard. In FIG. 5, theleft row shows the height of a light inputted to the objective lensdivided by the focal distance of the objective lens. And the right rowshows the number of steps of the phase filter pattern 6 b correspondingto the left row.

The multi layered dielectric film 7 f works to transmit all of the lighthaving wavelength of 405 nm and reflect all of the light havingwavelength of 650 nm. And also the multi layered dielectric film 7 fworks to make the phase difference of light, transmitting throughbetween within the circle of the diameter 2 e and outside the circle ofthe diameter 2 e, adjust to be integer times the value of 2%. That is,at the wavelength selective filter 3 c, the light having wavelength of405 nm is all transmitted, and the light having wavelength of 650 nm isall transmitted within the region of the circle of the diameter 2 e andis all reflected outside the region of the circle of the diameter 2 e.The effective numerical aperture for the light having wavelength of 405nm is set to be 0.7, and the effective numerical aperture for the lighthaving wavelength of 650 nm is set to be 0.6.

FIG. 6 is a graph showing the calculated result of the wavefrontaberration for the light having wavelength of 650 nm when the firstconventional optical head device was used at the interchangeabilitybetween the next generation standard and the conventional DVD standard.In FIG. 6 (a), a relation between the height of a light inputted to theobjective lens divided by the focal distance of the objective lens andthe wavefront aberration, at the best image position where the standarddeviation of the wavefront aberration becomes minimum, is shown, in acase that the wavelength selective filter 3 c was not used. And in FIG.6 (b), a relation between the height of a light inputted to theobjective lens divided by the focal distance of the objective lens andthe wavefront aberration, at the best image position where the standarddeviation of the wavefront aberration becomes minimum, is shown, in acase that the wavelength selective filter 3 c was used. As shown in FIG.6 (b), the standard deviation of the wavefront aberration is decreasedto be 0.054λ, by using the wavelength selective filter 3 c. This valueis lower than 0.07λ that is the allowable value of the standarddeviation of the wavefront aberration, known as Marechel's criterion.

However, as shown in FIG. 5, the number of regions of concentric circleshapes, of which the phase filter pattern 6 b is composed, is as many as19, and the width of each region becomes narrow. For example, when thefocal distance of the objective lens 4 b is decided to be 2.57 mm, thewidth of the most outside region becomes about 7.7 μm. Generally, anelement, whose cross-section has multi leveled step shapes, is formed bya photo lithography method, by using plural photo masks, however, whenthe plural photo masks are aligned with one another, there is an errorof 2 to 3 μm at each region. Therefore, it is very difficult tomanufacture such a wavelength selective filter having a phase filterpattern whose each region is very narrow mentioned above in desiringpreciseness.

As a second example, the change of the magnification of the objectivelens at the second conventional optical head device shown in FIG. 3 isstudied. In this case, the interchangeability between a next generationstandard, in which the wavelength of the light source is 405 nm, thenumerical aperture of the objective lens is 0.7, and the thickness ofthe disk substrate is 0.1 mm, and the conventional DVD standard isstudied. A semiconductor laser having wavelength of 405 nm is used torecord and reproduce information for the disk having thickness of 0.1 mmof the next generation standard. The semiconductor laser havingwavelength of 650 nm is used to record and reproduce information for thedisk having thickness of 0.6 mm of the DVD standard. The objective lens4 b has a spherical aberration, which cancels a spherical aberrationgenerated at the time when a light having wavelength of 405 nm, inputtedto the objective lens 4 b as a collimated light, transmits through thesubstrate having thickness of 0.1 mm.

The light having wavelength of 405 nm is inputted to the objective lens4 b as a collimated light, therefore, the magnification of the objectivelens 4 b for the light having wavelength of 405 nm is 0. On the otherhand, when the Light having wavelength of 650 nm, inputted to theobjective lens 4 b as a collimated light, was transmitted through thesubstrate having thickness of 0.6 mm, a spherical aberration remains.When the light having wavelength of 650 nm is inputted to the objectivelens 4 b as a diverged light, a new spherical aberration occurscorresponding to the change of the magnification of the objective lens 4b, and this new spherical aberration works to decrease the remainingspherical aberration. The magnification of the objective lens 4 b forthe light having wavelength of 650 nm is set to be 0.076.

The multi layered dielectric film 7 g at the aperture controllingelement 21 c works to transmit all of the light having wavelength of 405nm and reflect all of the light having wavelength of 650 nm. That is, atthe aperture controlling element 21 c, the light having wavelength of405 nm is all transmitted, and the light having wavelength of 650 nm isall transmitted within the region of the circle of the diameter 2 e andis all reflected outside the region of the circle of the diameter 2 e.The effective numerical aperture for the light having wavelength of 405nm is set to be 0.7, and the effective numerical aperture for the lighthaving wavelength of 650 nm is set to be 0.6. On the other hand, for thewavelength of 405 nm, the phase compensation film 28 works to adjust thephase difference of light transmitting through between within thecircular region and without the circular region to integer times thevalue of 2π.

FIG. 7 is a graph showing the calculated result of the wavefrontaberration for the light having wavelength of 650 nm when the secondconventional optical head device was used at the interchangeabilitybetween the next generation standard and the conventional DVD standard.In FIG. 7, a relation between the height of a light inputted to theobjective lens divided by the focal distance of the objective lens andthe wavefront aberration, at the best image position where the standarddeviation of the wavefront aberration becomes minimum for the lighthaving wavelength of 650 nm, is shown. The standard deviation of thewavefront aberration is decreased to be 0.095λ, by using the change ofthe magnification of the objective lens. However, this value is higherthan 0.07λ that is the allowable value of the standard deviation of thewavefront aberration, known as Marechel's criterion.

It can be considered to combine the wavelength selective filter at thefirst conventional optical head device shown in FIG. 1 with the changeof the magnification of the objective lens at the second conventionaloptical head device shown in FIG. 3, in order to meet theinterchangeability between the next generation standard and theconventional DVD standard.

However, at this combined case, in the phase filter pattern at thewavelength selective filter, it is designed that the change of the phasedistribution for the light having wavelength of 650 nm decreases thespherical aberration that remains at the time when the light havingwavelength of 650 nm, inputted to the objective lens as a collimatedlight, transmits through the substrate having thickness of 0.6 mm.Consequently, the spherical aberration, which remains at the time whenthe light having wavelength of 650 nm, inputted to the objective lens asa diverged light, transmits through the substrate having thickness of0.6 mm, is not decreased by using the wavelength selective filter, andon the contrary, is increased.

As mentioned above, when the wavelength of the light source is short andthe numerical aperture of the objective lens becomes high, there areproblems that the wavelength selective filter at the first conventionaloptical head device shown in FIG. 1 and the change of the magnificationof the objective lens at the second conventional optical head deviceshown in FIG. 3 can not be used for the interchangeability.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide an opticalhead device and an optical recording and reproducing apparatus usingthis optical head device, which records information and reproduces therecorded information at plural types of optical recording media in whichthe thickness of substrates of the optical recording media is differentfrom one another. Further, an optical head device and an opticalrecording and reproducing apparatus using this optical head device,which has the interchangeability between a next generation opticalrecording medium, in which the wavelength of the light source is made tobe much shorter, the numerical aperture of the objective lens is made tobe much higher, and the thickness of the optical recording medium ismade to be much thinner, in order to make the recording density high,and the conventional recording media of the DVD and CD standards, areprovided.

According to a first aspect of the present invention, for achieving theobject mentioned above, there is provided an optical head device. Theoptical head device provides a first light source for emitting a lighthaving a first wavelength, a second light source for emitting a lighthaving a second wavelength, a photo detector, a wavelength selectivefilter, and an objective lens. And an optical system is formed by that alight emitted form the first light source is transmitted to a firstoptical recording medium containing a first substrate having a firstthickness through the wavelength selective filter and the objectivelens, a light emitted form the second light source is transmitted to asecond optical recording medium containing a second substrate having asecond thickness through the wavelength selective filter and theobjective lens, a light reflected from the first optical recordingmedium is transmitted to the photo detector through the objective lensand the wavelength selective filter, and a light reflected from thesecond optical recording medium is transmitted to the photo detectorthrough the objective lens and the wavelength selective filter. Andrecording and reproducing information is executed for the first opticalrecording medium by using the light having the first wavelength, andrecording and reproducing information is executed fox the second opticalrecording medium by using the light having the second wavelength. Andthe magnification of the objective lens for the light having the firstwavelength is different from the magnification of the objective lens forthe light having the second wavelength, and the wavelength selectivefilter changes the phase distribution so that a spherical aberrationremaining for the light having the first wavelength or the light havingthe second wavelength at corresponding the magnification of theobjective lens is decreased.

According to a second aspect of the present invention, in the firstaspect, the first wavelength is shorter than the second wavelength.

According to a third aspect of the present invention, in the firstaspect, the first thickness of the first substrate is thinner than thesecond thickness of the second substrate.

According to a fourth aspect of the present invention, in the firstaspect, the objective lens has a spherical aberration that cancels aspherical aberration generated at the time when the light having thefirst wavelength, inputted to the objective lens as a collimated light,transmits through the first substrate having the first thickness.

According to a fifth aspect of the present invention, in the firstaspect, the light emitted from the first light source is inputted to theobjective lens as an almost collimated light so that the magnificationof the objective lens for the light having the first wavelength becomesabout 0, and the light emitted from the second light source is inputtedto the objective lens as a diverged light so that the magnification ofthe objective lens for the light having the second wavelength becomes afirst designated value.

According to a sixth aspect of the present invention, in the firstaspect, the wavelength selective filter provides a phase filter patternhaving concentric circle shapes, and first and second multi layereddielectric films.

According to a seventh aspect of the present invention, in the sixthaspect, the phase filter pattern hardly changes the phase distributionfor the light having the first wavelength, and changes the phasedistribution for the light having the second wavelength.

According to an eighth aspect of the present invention, in the sixthaspect, the phase filter pattern is designed so that the change of thephase distribution for the light having the second wavelength decreasesa spherical aberration at the magnification of the first designatedvalue of the objective lens.

According to a ninth aspect of the present invention, in the sixthaspect, the phase filter pattern is formed only within a circular regionhaving a first diameter that is smaller than the effective diameter ofthe objective lens.

According to a tenth aspect of the present invention, in the sixthaspect, the cross-section of the phase filter pattern has a multi levelstep shape.

According to an eleventh aspect of the present invention, in the tenthaspect, the height of each step of the phase filter pattern is set to bea value so that the phase difference of light transmitting throughbetween a part with a pattern and a part without a pattern at each stepbecomes about 2π for the first wavelength.

According to a twelfth aspect of the present invention, in the ninthaspect, the first multi layered dielectric film is formed only withinthe circular region having the first diameter, and the second multilayered dielectric film is formed only outside the circular regionhaving the first diameter.

According to a thirteenth aspect of the present invention, in thetwelfth aspect, the first multi layered dielectric film transmits almostall the light having the first wavelength and almost all the lighthaving the second wavelength, and the second multi layered dielectricfilm transmits almost all the light having the first wavelength andreflects almost all the light having the second wavelength.

According to a fourteenth aspect of the present invention, in thetwelfth aspect, the phase difference of the light having the firstwavelength transmitting through between the first multi layereddielectric film and the second multi layered dielectric film is adjustedto be about integer times the value of 2π.

According to a fifteenth aspect of the present invention, in the sixthaspect, each of the first and second multi layered dielectric films hasa structure in which a high refractive index layer and a low refractiveindex layer are layered alternately.

According to a sixteenth aspect of the present invention, in thefifteenth aspect, the thickness of each layer of the first multi layereddielectric film is different from the thickness of each layer of thesecond multi layered dielectric film.

According to a seventeenth aspect of the present invention, in the sixthaspect, the phase filter pattern is formed on a first glass substrate,and the first and second multi layered dielectric films are formed on asecond glass substrate.

According to an eighteenth aspect of the present invention, in theseventeenth aspect, a surface, where the phase filter pattern was notformed, of the first glass substrate, and a surface, where the first andsecond multi layered dielectric films were not formed, of the secondglass substrate, are adhered by an adhesive.

According to a nineteenth aspect of the present invention, in theseventeenth aspect, the phase filter pattern is formed by being unifiedwith the first glass substrate by glass forming, or by using a plasticfor the first glass substrate instead of glass, and the phase filterpattern is formed by being unified with a plastic substrate by plasticmolding.

According to a twentieth aspect of the present invention, in the sixthaspect, the phase filter pattern and/or the first and second multilayered dielectric films are formed on the objective lens.

According to a twenty-first aspect of the present invention, in thefirst aspect, the optical head device further provides a third lightsource for emitting a light having a third wavelength. And further anadditional optical system is formed by that a light emitted form thethird light source is transmitted to a third optical recording mediumcontaining a third substrate having a third thickness through thewavelength selective filter and the objective lens, a light reflectedfrom the third optical recording medium is transmitted to the photodetector through the objective lens and the wavelength selective filter.And recording and reproducing information is executed for the thirdoptical recording medium by using the light having the third wavelength,and the magnification of the objective lens for the light having thethird wavelength is different from the magnification of the objectivelens for the light having the first wavelength.

According to a twenty-second aspect of the present invention, in thetwenty-first aspect, the first wavelength is shorter than the secondwavelength, and the second wavelength is shorter than the thirdwavelength.

According to a twenty-third aspect of the present invention, in thetwenty-first aspect, the first thickness of the first substrate isthinner than the second thickness of the second substrate, and thesecond thickness of the second substrate is thinner than the thirdthickness of the third substrate.

According to a twenty-fourth aspect of the present invention, in thetwenty-first aspect, the objective lens has a spherical aberration thatcancels a spherical aberration generated at the time when the lighthaving the first wavelength, inputted to the objective lens as acollimated light, transmits through the first substrate having the firstthickness.

According to a twenty-fifth aspect of the present invention, in thetwenty-first aspect, the light emitted from the first light source isinputted to the objective lens as an almost collimated light so that themagnification of the objective lens for the light having the firstwavelength becomes about 0, the light emitted from the second lightsource is inputted to the objective lens as a diverged light so that themagnification of the objective lens for the light having the secondwavelength becomes a first designated value, and the light emitted fromthe third light source is inputted to the objective lens as a divergedlight so that the magnification of the objective lens for the lighthaving the third wavelength becomes a second designated value.

According to a twenty-sixth aspect of the present invention, in thetwenty-first aspect, the wavelength selective filter provides a phasefilter pattern haying concentric circle shapes, and first, second, andthird multi layered dielectric films.

According to a twenty-seventh aspect of the present invention, in thetwenty-sixth aspect, the phase filter pattern hardly changes the phasedistribution for the light having the first wavelength, and changes thephase distribution for the light having the second wavelength and thethird wavelength.

According to a twenty-eighth aspect of the present invention, in thetwenty-sixth aspect, the phase filter pattern is designed so that thechange of the phase distribution for the light having the secondwavelength decreases a spherical aberration at the magnification of thefirst designated value of the objective lens.

According to a twenty-ninth aspect of the present invention, in thetwenty-sixth aspect, the phase filter pattern is formed only within acircular region having a first diameter that is smaller than theeffective diameter of the objective lens.

According to a thirtieth aspect of the present invention, in thetwenty-sixth aspect, the cross-section of the phase filter pattern has amulti level step shape.

According to a thirty-first aspect of the present invention, in thethirtieth aspect, the height of each step of the phase filter pattern isset to be a value so that the phase difference of light transmittingthrough between a part with a pattern and a part without a pattern ateach step becomes about 2 it for the first wavelength.

According to a thirty-second aspect of the present invention, in thetwenty-ninth aspect, the first multi layered dielectric film is formedonly within a circular region having a second diameter which is smallerthan the first diameter, the second multi layered dielectric film isformed only outside the circular region having the second diameter andalso within the circular region having the first diameter, and the thirdmulti layered dielectric film is formed only outside the circular regionhaving the first diameter.

According to a thirty-third aspect of the present invention, in thethirty-second aspect, the first multi layered dielectric film transmitsalmost all the light having the first wavelength, almost all the lighthaving the second wavelength, and almost all the light having the thirdwavelength, the second multi layered dielectric film transmits almostall the light having the first wavelength and almost all the lighthaving the second wavelength, and reflects almost all the light havingthe third wavelength, and the third multi layered dielectric filmtransmits almost all the light having the first wavelength, and reflectsalmost all the light having the second wavelength and almost all thelight having the third wavelength.

According to a thirty-fourth aspect of the present invention, in thethirty-second aspect, the phase difference of the light having the firstwavelength transmitting through between the first multi layereddielectric film and the second multi layered dielectric film is adjustedto be about integer times the value of 2π, the phase difference of thelight having the first wavelength transmitting through between thesecond multi layered dielectric film and the third multi layereddielectric film is adjusted to be about integer times the value of 2π,and the phase difference of the light having the second wavelengthtransmitting through between the first multi layered dielectric film andthe second multi layered dielectric film is adjusted to be about integertimes the value of 2π.

According to a thirty-fifth aspect of the present invention, in thetwenty-sixth aspect, each of the first, second, and third multi layereddielectric films has a structure in which a high refractive index layerand a low refractive index layer are layered alternately.

According to a thirty-sixth aspect of the present invention, in thethirty-fifth aspect, the thickness of each layer and the number oflayers of the first multi layered dielectric film are different from,the thickness of each layer and the number of layers of the second multilayered dielectric film, and the thickness of each layer of the secondmulti layered dielectric film is different from the thickness of eachlayer of the third multi layered dielectric film.

According to a thirty-seventh aspect of the present invention, in thetwenty-sixth aspect, the phase filter pattern is formed on a first glasssubstrate, and the first, second, and third multi layered dielectricfilms are formed on a second glass substrate.

According to a thirty-eighth aspect of the present invention, in thethirty-seventh aspect, a surface, where the phase filter pattern was notformed, of the first glass substrate, and a surface, where the first,second, and third multi layered dielectric films were not formed, of thesecond glass substrate, axe adhered by an adhesive.

According to a thirty-ninth aspect of the present invention, in thethirty-seventh aspect, the phase filter pattern is formed by beingunified with the first glass substrate by glass forming, or by using aplastic for the first glass substrate instead of glass, and the phasefilter pattern is formed by being unified with a plastic substrate byplastic molding.

According to a fortieth aspect of the present invention, in thetwenty-sixth aspect, the phase filter pattern, and/or the first, second,and third multi layered dielectric films are formed on the objectivelens.

According to a forty-first aspect of the present invention, there isprovided an optical head device. The optical head device provides afirst light source for emitting a light having a first wavelength, asecond light source for emitting a light having a second wavelength, aphoto detector, an aperture controlling element, and an objective lens.And an optical system is formed by that a light emitted form the firstlight source is transmitted to a first optical recording mediumcontaining a first substrate having a first thickness through theaperture controlling element and the objective lens, a fight emittedform the second light source is transmitted to a second opticalrecording medium containing a second substrate having a second thicknessthrough the aperture controlling element and the objective lens, a lightreflected from the first optical recording medium is transmitted to thephoto detector through the objective lens and the aperture controllingelement, and a light reflected from the second optical recording mediumis transmitted to the photo detector through the objective lens and theaperture controlling element. And recording and reproducing informationis executed for the first optical recording medium by using the lighthaving the first wavelength, and recording and reproducing informationis executed for the second optical recording medium by using the fighthaving the second wavelength. And the magnification of the objectivelens for the light having the first wavelength is different from themagnification of the objective lens for the light having the secondwavelength. And the optical head device further provides a firstspherical aberration correcting element disposed between the objectivelens and the first light source or the second light source. And thefirst spherical aberration correcting element changes the phasedistribution so that a spherical aberration remaining for the lighthaving the first wavelength or the light having the second wavelength atcorresponding the magnification of the objective lens is corrected.

According to a forty-second aspect of the present invention, in theforty-first aspect, the first wavelength is shorter than the secondwavelength.

According to a forty-third aspect of the present invention, in theforty-first aspect, the first thickness of the first substrate isthinner than the second thickness of the second substrate.

According to a forty-fourth aspect of the present invention, in theforty-first aspect, the objective lens has a spherical aberration thatcancels a spherical aberration generated at the time when the lighthaving the first wavelength, inputted to the objective lens as acollimated light, transmits through the first substrate having the firstthickness.

According to a forty-fifth aspect of the present invention, in theforty-first aspect, the light emitted from the first light source isinputted to the objective lens as an almost collimated light so that themagnification of the objective lens for the light having the firstwavelength becomes about 0, and the light emitted from the second lightsource is inputted to the objective lens as a diverged light so that themagnification of the objective lens for the light having the secondwavelength becomes a first designated value.

According to a forty-sixth aspect of the present invention, in theforty-first aspect, the aperture controlling element provides first andsecond multi layered dielectric films.

According to a forty-seventh aspect of the present invention, in theforty-sixth aspect, the first multi layered dielectric film is formedonly within a circular region having a first diameter that is smallerthan the effective diameter of the objective lens, and the second multilayered dielectric film is formed only outside the circular regionhaving the first diameter.

According to a forty-eighth aspect of the present invention, in theforty-seventh aspect, the first multi layered dielectric film transmitsalmost all the light having the first wavelength and almost all thelight having the second wavelength, and the second multi layereddielectric film transmits almost all the light having the firstwavelength and reflects almost all the light having the secondwavelength.

According to a forty-ninth aspect of the present invention, in theforty-eighth aspect, the phase difference of the light having the firstwavelength transmitting through between the first multi layereddielectric film and the second multi layered dielectric film is adjustedto be about integer times the value of 2π.

According to a fiftieth aspect of the present invention, in theforty-sixth aspect, each of the first and second multi layereddielectric films has a structure in which a high refractive index layerand a low refractive index layer are layered alternately.

According to a fifty-first aspect of the present invention, in theforty-sixth aspect, the first and second multi layered dielectric filmsare formed on a glass substrate.

According to a fifty-second aspect of the present invention, in theforty-sixth aspect, the first and second multi layered dielectric filmsare formed on the objective lens.

According to a fifty-third aspect of the present invention, in theforty-first aspect, the first spherical aberration correcting element isdisposed between the aperture controlling element and the second lightsource, and changes the phase distribution for the fight having thesecond wavelength.

According to a fifty-fourth aspect of the present invention, in thefifty-third aspect, the first spherical aberration correcting element isdesigned so that the change of the phase distribution for the lighthaving the second wavelength corrects a spherical aberration at themagnification of the first designated value of the objective lens.

According to a fifty-fifth aspect of the present invention, in thefifty-third aspect, one of surfaces of the first spherical aberrationcorrecting element is a plane and the other of the surfaces is anaspherical surface.

According to a fifty-sixth aspect of the present invention, in thefifty-third aspect, the first spherical aberration correcting element isunified with a first lens.

According to a fifty-seventh aspect of the present invention, in theforty-first aspect, a coma aberration caused by that the center of theobjective lens deviates from the center of the first sphericalaberration correcting element is corrected by inclining the objectivelens in the radial direction of the second optical recording medium.

According to a fifty-eighth aspect of the present invention, in theforty-first aspect, first and second relay lenses are disposed betweenthe first and second light sources and the aperture controlling element.

According to a fifty-ninth aspect of the present invention, in thefifty-eighth aspect, a spherical aberration caused by the deviation ofthe first thickness of the first substrate of the first opticalrecording medium is corrected by moving one of the first and secondrelay lenses in the optical axis direction.

According to a sixtieth aspect of the present invention, in thefifty-eighth aspect, a coma aberration caused by that the center of theobjective lens deviates from the center of the first sphericalaberration correcting element is corrected by inclining or moving one ofthe first and second relay lenses in the radial direction of the secondoptical recording medium.

According to a sixty-first aspect of the present invention, in thesixtieth aspect, one of the first and second relay lenses is designednot to satisfy the sine condition.

According to a sixty-second aspect of the present invention, in theforty-first aspect, the optical head device further provides a thirdlight source for emitting a light having a third wavelength. And furtheran additional optical system is formed by that a light emitted form thethird light source is transmitted to a third optical recording mediumcontaining a third substrate having a third thickness through theaperture controlling element and the objective lens, and a lightreflected from the third optical recording medium is transmitted to thephoto detector through the objective lens and the aperture controllingelement. And recording and reproducing information is executed for thethird optical recording medium by using the light having the thirdwavelength. And the magnification of the objective lens for the fighthaving the third wavelength is different from the magnification of theobjective lens for the light having the first wavelength. And opticalhead device further provides a second spherical aberration correctingelement disposed between the aperture controlling element and the firstlight source or the third light source. And the second sphericalaberration correcting element changes the phase distribution so that aspherical aberration remaining for the light having the first wavelengthor the light having the third wavelength at corresponding themagnification of the objective lens is corrected.

According to a sixty-third aspect of the present invention, in thesixty-second aspect, the first wavelength is shorter than the secondwavelength, and the second wavelength is shorter than the thirdwavelength.

According to a sixty-fourth aspect of the present invention, in thesixty-second aspect, the first thickness of the first substrate isthinner than the second thickness of the second substrate, and thesecond thickness of the second substrate is thinner than the thirdthickness of the third substrate.

According to a sixty-fifth aspect of the present invention, in thesixty-second aspect, the objective lens has a spherical aberration thatcancels a spherical aberration generated at the time when the lighthaving the first wavelength, inputted to the objective lens as acollimated light, transmits through the first substrate having the firstthickness.

According to a sixty-sixth aspect of the present invention, in thesixty-second aspect, the light emitted from the first light source isinputted to the objective lens as an almost collimated light so that themagnification of the objective lens for the light having the firstwavelength becomes about 0, the light emitted from the second lightsource is inputted to the objective lens as a diverged light so that themagnification of the objective lens for the light having the secondwavelength becomes a first designated value, and the light emitted fromthe third light source is inputted to the objective lens as a divergedlight so that the magnification of the objective lens for the fighthaving the third wavelength becomes a second designated value.

According to a sixty-seventh aspect of the present invention, in thesixty-second aspect, the aperture controlling element provides first,second, and third multi layered dielectric films.

According to a sixty-eighth aspect of the present invention, in thesixty-seventh aspect, the first multi layered dielectric film is formedonly within a circular region having a second diameter which is smallerthan a first diameter being smaller than the effective diameter of theobjective lens, the second multi layered dielectric film is formed onlyoutside the circular region having the second diameter and also withinthe circular region having the first diameter, and the third multilayered dielectric film is formed only outside the circular regionhaving the first diameter.

According to a sixty-ninth aspect of the present invention, in thesixty-seventh aspect, the first multi layered dielectric film transmitsalmost all the light having the first wavelength, almost all the lighthaving the second wavelength, and almost all the light having the thirdwavelength, the second multi layered dielectric film transmits almostall the light having the first wavelength and almost all the lighthaving the second wavelength, and reflects almost all the light havingthe third wavelength, and the third multi layered dielectric filmtransmits almost all the light having the first wavelength, and reflectsalmost all the light having the second wavelength and almost all thelight having the third wavelength.

According to a seventieth aspect of the present invention, in thesixty-seventh aspect, the phase difference of the light having the firstwavelength transmitting through between the first multi layereddielectric film and the second multi layered dielectric film is adjustedto be about integer times the value of 2π, the phase difference of thelight having the first wavelength transmitting through between thesecond multi layered dielectric film and the third multi layereddielectric film is adjusted to be about integer times the value of 2π,and the phase difference of the light having the second wavelengthtransmitting through between the first multi layered dielectric film andthe second multi layered dielectric film is adjusted to be about integertimes the value of 2π.

According to a seventy-first aspect of the present invention, in thesixty-seventh aspect, each of the first, second, and third multi layereddielectric films has a structure in which a high refractive index layerand a low refractive index layer are layered alternately.

According to a seventy-second aspect of the present invention, in thesixty-seventh aspect, the first, second, and third multi layereddielectric films are formed on a glass substrate.

According to a seventy-third aspect of the present invention, in thesixty-seventh aspect, the first, second, and third multi layereddielectric films are formed on the objective lens.

According to a seventy-fourth aspect of the present invention, in thesixty-sixth aspect, the first spherical aberration correcting element isdisposed between the aperture controlling element and the second lightsource, and changes the phase distribution for the light having thesecond wavelength, and the second spherical aberration correctingelement is disposed between the aperture controlling element and thethird light source, and changes the phase distribution for the lighthaving the third wavelength.

According to a seventy-fifth aspect of the present invention, in theseventy-fourth aspect, the first spherical aberration correcting elementis designed so that the change of the phase distribution for the lighthaving the second wavelength corrects a spherical aberration at themagnification of the first designated value of the objective lens, andthe second spherical aberration correcting element is designed so thatthe change of the phase distribution for the light having the thirdwavelength corrects a spherical aberration at the magnification of thesecond designated value of the objective lens.

According to a seventy-sixth aspect of the present invention, in theseventy-fourth aspect) one of surfaces of the first and second sphericalaberration correcting elements is a plane and the other of the surfacesis an aspherical surface.

According to a seventy-seventh aspect of the present invention, in theseventy-fourth aspect, the first spherical aberration correcting elementis unified with a first lens, and the second spherical aberrationcorrecting element is unified with a second lens.

According to a seventy-eighth aspect of the present invention, in thesixty-second aspect, a coma aberration caused by that the center of theobjective lens deviates from the center of the first sphericalaberration correcting element is corrected by inclining the objectivelens in the radial direction of the second optical recording medium, anda coma aberration caused by that the center of the objective lensdeviates from the center of the second spherical aberration correctingelement is corrected by inclining the objective lens in the radialdirection of the third optical recording medium.

According to a seventy-ninth aspect of the present invention, in thesixty-second aspect, first and second relay lenses are disposed betweenthe first, second, and third light sources and the aperture controllingelement.

According to an eightieth aspect of the present invention, in theseventy-ninth aspect, a spherical aberration caused by the deviation ofthe first thickness of the first substrate of the first opticalrecording medium is corrected by moving one of the first and secondrelay lenses in the optical axis direction.

According to an eighty-first aspect of the present invention, in theseventy-ninth aspect, a coma aberration caused by that the center of theobjective lens deviates from the center of the first sphericalaberration correcting element is corrected by inclining or moving one ofthe first and second relay lenses in the radial direction of the secondoptical recording medium, and a coma aberration caused by that thecenter of the objective lens deviates from the center of the secondspherical aberration correcting element is corrected by inclining ormoving one of the first and second relay lenses in the radial directionof the third optical recording medium.

According to an eighty-second aspect of the present invention, in theeighty-first aspect, one of the first and second relay lenses isdesigned not to satisfy the sine condition.

According to an eighty-third aspect of the present invention, there isprovided an optical recording and reproducing apparatus. The opticalrecording and reproducing apparatus provides an optical head deviceclaimed in the claims 1 to 20 or claims 41 to 61, a recording andreproducing circuit, which generates input signals to light sourcesbased on recording signals to optical recording media and also generatesreproducing Signals from the optical recording media based on outputsignals from a photo detector, a switching circuit, which switchestransmission routes of the input signals to one of the transmissionroutes, and a controlling circuit, which controls the operation of theswitching circuit corresponding to the kinds of optical recording media.

According to an eighty-fourth aspect of the present invention, in theeighty-third aspect, the recording and reproducing circuit provides afirst recording and reproducing circuit, which generates a first inputsignal to a first light source based on a recording signal to a firstoptical recording medium and also generates a reproducing signal fromthe first optical recording medium based on an output signal from aphoto detector, and a second recording and reproducing circuit, whichgenerates a second input signal to a second light source based on arecording signal to a second optical recording medium and also generatesa reproducing signal from the second optical recording medium based onan output signal from a photo detector. And the switching circuitswitches the transmission routes to one of the transmission route whichare a transmission route of the first input signal from the firstrecording and reproducing circuit to the first light source and atransmission route of the second input signal from the second recordingand reproducing circuit to the second fight source, and the controllingcircuit controls the operation of the switching circuit so that thefirst input signal is transmitted from the first recording andreproducing circuit to the first light source when the first opticalrecording medium was inserted, and the second input signal istransmitted from the second recording and reproducing circuit to thesecond light source when the second optical recording medium wasinserted.

According to an eighty-fifth aspect of the present invention, in theeighty-third aspect, the recording and reproducing circuit is a singlerecording and reproducing circuit, the single recording and reproducingcircuit generates first and second input signals to first and secondlight sources based on recording signals to first and second opticalrecording media respectively, and also generates reproducing signalsfrom the first and second optical recording media based on outputsignals from a photo detector, the switching circuit switches thetransmission routes to one of the transmission routes which are atransmission route of the first input signal from the single recordingand reproducing circuit to the first light source and a transmissionroute of the second input signal from the single recording andreproducing circuit to the second light source, and the controllingcircuit controls the operation of the switching circuit so that thefirst input signal is transmitted from the single recording andreproducing circuit to the first light source when the first opticalrecording medium was inserted, and the second input signal istransmitted from the single recording and reproducing circuit to thesecond light source when the second optical recording medium wasinserted.

According to an eighty-sixth aspect of the present invention, there isprovided an optical recording and reproducing apparatus. The opticalrecording and reproducing apparatus provides an optical head deviceclaimed in the claims 21 to 40 or claims 62 to 82, a recording andreproducing circuit, which generates input signals to light sourcesbased on recording signals to optical recording media and also generatesreproducing signals from the optical recording media based on outputsignals from a photo detector, a switching circuit, which switchestransmission routes of the input signals to one of the transmissionroutes, and a controlling circuit, which controls the operation of theswitching circuit corresponding to the kinds of optical recording media.

According to an eighty-seventh aspect of the present invention, in theeighty-sixth aspect, the recording and reproducing circuit provides afirst recording and reproducing circuit, which generates a first inputsignal to a first light source based on a recording signal to a firstoptical recording medium and also generates a reproducing signal fromthe first optical recording medium based on an output signal from aphoto detector, a second recording and reproducing circuit, whichgenerates a second input signal to a second light source based on arecording signal to a second optical recording medium and also generatesa reproducing signal from the second optical recording medium based onan output signal from a photo detector, and a third recording andreproducing circuit, which generates a third input signal to a thirdlight source based on a recording signal to a third optical recordingmedium and also generates a reproducing signal from the third opticalrecording medium based on an output signal from a photo detector. Andthe switching circuit switches the transmission routes to one of thetransmission routes which are a transmission route of the first inputsignal from the first recording and reproducing circuit to the firstfight source, a transmission route of the second input signal from thesecond recording and reproducing circuit to the second light source, anda transmission route of the third input signal from the third recordingand reproducing circuit to the third light source, the controllingcircuit controls the operation of the switching circuit so that thefirst input signal is transmitted from the first recording andreproducing circuit to the first light source when the first opticalrecording medium was inserted, and the second input signal istransmitted from the second recording and reproducing circuit to thesecond light source when the second optical recording medium wasinserted, and the third input signal is transmitted from the thirdrecording and reproducing circuit to the third light source when thethird optical recording medium was inserted.

According to an eighty-eighth aspect of the present invention, in theeighty-sixth aspect, the recording and reproducing circuit is a singlerecording and reproducing circuit, the single recording and reproducingcircuit generates first, second, and third input signals to first,second, and third light sources based on recording signals to first,second, and third optical recording media respectively, and alsogenerates reproducing signals from the first, second, and third opticalrecording media based on output signals from a photo detector, theswitching circuit switches the transmission routes to one of thetransmission routes which are a transmission route of the first inputsignal from the single recording and reproducing circuit to the firstlight source, a transmission route of the second input signal from thesingle recording and reproducing circuit to the second light source, anda transmission route of the third input signal from the single recordingand reproducing circuit to the third light source, and the controllingcircuit controls the operation of the switching circuit so that thefirst input signal is transmitted from the single recording andreproducing circuit to the first light source when the first opticalrecording medium was inserted, and the second input signal istransmitted from the single recording and reproducing circuit to thesecond light source when the second optical recording medium wasinserted, and the third input signal is transmitted from the singlerecording and reproducing circuit to the third light source when thethird optical recording medium was inserted.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects and features of the present invention will become moreapparent from the consideration of the following detailed descriptiontaken in conjunction with the accompanying drawings in which:

FIG. 1 is a block diagram showing a structure of an optical head deviceat Japanese Patent Application Laid-Open No. HEI 10-334504;

FIG. 2 is a diagram showing a wavelength selective filter shown in FIG.1;

FIG. 3 is a block diagram showing a structure of an optical head deviceat Japanese Patent Application Laid-Open No. HEI 9-274730;

FIG. 4 is a diagram showing an aperture controlling element shown inFIG. 3);

FIG. 5 is a table showing a designed result of a phase filter patternwhen the phase filter pattern of a first conventional optical headdevice was used at the interchangeability between a next generationstandard and the conventional DVD standard;

FIG. 6 is a graph showing a calculated result of the wavefrontaberration for the light having wavelength of 650 nm when the firstconventional optical head device was used at the interchangeabilitybetween the next generation standard and the conventional DVD standard;

FIG. 7 is a graph showing a calculated result of the wavefrontaberration for the light having wavelength of 650 nm when a secondconventional optical head device was used at the interchangeabilitybetween the next generation standard and the conventional DVD standard;

FIG. 8 is a block diagram showing a structure of a first embodiment ofan optical head device of the present invention;

FIG. 9 is a diagram showing a wavelength selective filter shown in FIG.8;

FIG. 10A is a block diagram shearing a structure of an optics shown inFIG. 8;

FIG. 10B is a diagram showing a structure of a photo detector in theoptics shown in FIG. 10A;

FIG. 11A is a diagram showing a structure of the other optics 75 shownin FIG. 8;

FIG. 11B is a diagram showing a structure of a photo detector in theother optics shown in FIG. 11A;

FIG. 12 is a table showing a designed result of a phase filter patternin the wavelength selective filter shown in FIG. 8;

FIG. 13 is a graph showing a calculated result of the wavefrontaberration for the light having wavelength of 650 nm at the firstembodiment of the optical head device of the present invention;

FIG. 14A is a graph showing a designed result of a wavelength dependencyof the transmittance for multi layered dielectric films in thewavelength selective filter at the embodiments of the Optical headdevice of the present invention;

FIG. 14B is a graph showing a designed result of a wavelength dependencyof the phase of transmitted light through the multi layered dielectricfilms in the wavelength selective filter at the embodiments of theoptical head device of the present invention;

FIG. 15 is a block diagram showing a structure of a second embodiment ofthe optical head device of the present invention;

FIG. 16 is a diagram showing a wavelength selective filter shown in FIG.15;

FIG. 17A is a block diagram showing a structure of an optics shown inFIG. 15;

FIG. 17B is a diagram showing a structure of a photo detector in theoptics shown in FIG. 17A;

FIG. 18 is a graph showing a calculated result of the wavefrontaberration for the fight having wavelength of 780 nm at the secondembodiment of the optical head device of the present invention;

FIG. 19 is a block diagram showing a structure of a third embodiment ofthe optical head device of the present invention;

FIG. 20 is a diagram showing an aperture controlling element shown inFIG. 19;

FIG. 21 is a diagram showing a structure of an optics shown in

FIG. 19;

FIG. 22 is a block diagram showing a structure of a fourth embodiment ofthe optical head device of the present invention;

FIG. 23 is a diagram showing an aperture controlling element shown inFIG. 22;

FIG. 24 is a diagram showing a structure of an optics shown in

FIG. 22;

FIG. 25 is a block diagram showing a structure of a fifth embodiment ofthe optical head device of the present invention;

FIG. 26 is a block diagram showing a structure of a sixth embodiment ofthe optical head device of the present invention;

FIG. 27 is a block diagram showing a structure of a first embodiment ofan optical recording and reproducing apparatus of the present invention;

FIG. 28 is a block diagram showing a structure of a second embodiment ofthe optical recording and reproducing apparatus of the presentinvention;

FIG. 29 is a block diagram showing a structure of a third embodiment ofthe optical recording and reproducing apparatus of the presentinvention; and

FIG. 30 is a block diagram showing a structure of a fourth embodiment ofthe optical recording and reproducing apparatus of the presentinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings, embodiments of the present invention areexplained in detail. First a first embodiment of an optical head deviceof the present invention is explained.

FIG. 8 is a block diagram showing a structure of the first embodiment ofthe optical head device of the present invention.

In FIG. 8, each of optics 1 a and 1 b provides a semiconductor laser anda photo detector that receives a light reflected from one of disks. Thewavelength of the semiconductor laser in the optics 1 a is 405 nm, andthe wavelength of the semiconductor laser in the optics 1 b is 650 nm.

An interference filter 2 f works to transmit a light having wavelengthof 405 nm and reflect a light having wavelength of 650 nm. A lightemitted from the semiconductor laser in the optics 1 a transmits theinterference filter 2 f and a wavelength selective filter 3 a. And thetransmitted light is inputted to an objective lens 4 a as a collimatedlight and is focused on a disk 5 a, whose thickness is 0.1 mm, of a nextgeneration standard. A light reflected from the disk 5 a transmits theobjective lens 4 a, the wavelength selective filter 3 a, and theinterference filter 2 f in the inverse direction, and the photo detectorin the optics 1 a receives the transmitted light.

A light emitted from the semiconductor laser in the optics 1 b isreflected at the interference filter 2 f and the reflected lighttransmits the wavelength selective filter 3 a. And the transmitted lightis inputted to the objective lens 4 a as a diverged light, and isfocused on a disk 3 b, whose thickness is 0.6 mm, of the DVD standard. Alight reflected from the disk 5 b transmits the objective lens 4 a, thewavelength selective filter 3 a in the inverse direction, and isreflected at the interference filter 2 f, and the photo detector in theoptics 1 b receives the transmitted light.

The objective lens 4 a has a spherical aberration, which cancels aspherical aberration generated at the time when the light, whosewavelength is 405 nm, transmits through the disk 5 a whose thickness is0.1 mm. The light having wavelength of 405 nm is inputted to theobjective lens 4 a as the collimated light, therefore, the magnificationof the objective lens 4 a for the light having wavelength of 405 nm is0.

At the time when the light having wavelength of 650 nm, inputted to theobjective lens 4 a as the collimated light, transmits through the disk 5b having thickness of 0.6 mm, a spherical aberration remains. When thelight having wavelength of 650 nm is inputted to the objective lens 4 aas the diverged light, a new spherical aberration, corresponding to thechange of the magnification of the objective lens 4 a, is generated, andthis new spherical aberration works to decrease the remaining sphericalaberration. The magnification, of the objective lens 4 a for the lighthaving wavelength of 650 nm is set to be 0.076.

In this, when an angle, between a paraxial ray, which goes from anobject point to a designated height “r” of the objective lens 4 a, andthe optical axis of the objective lens 4 a, is defined as θo, and anangle, between a paraxial ray, which goes from the designated height “r”of the objective lens 4 a to an image point, and the optical axis of theobjective lens 4 a, is defined as θi, the magnification of the objectivelens 4 a is given as tan θo/tan θi.

When the length, from the object point to the principal point of theobject side of the objective lens 4 a, is defined as lo, and the length,from the principal point of the image side of the objective lens 4 a tothe image point, is defined as li, the tan θo= r/lo, and the tanθi=r/li. The light having wavelength of 405 nm is inputted to theobjective lens 4 a as the collimated light, therefore, the θo=0, and thelo=∞, and the magnification of the objective lens 4 a becomes 0. Thelight having wavelength of 650 nm is inputted to the objective leas 4 aas the diverged light, therefore, the θo≠0, and the lo is finite. Atthis time, the value of the lo, that is, the position of the objectpoint, is decided so that the magnification of the objective lens 4 abecomes 0.076.

FIG. 9 is a diagram showing the wavelength selective filter 3 a shown inFIG. 8. In FIG. 9 (a), the plane view of the wavelength selective filter3 a, looking from the upper side, is shown, in FIG. 9 (b), the planeview of the wavelength selective filter 8 a, looking from the bottomside, is shown, and in FIG. 9 (c), the sectional view of the wavelengthselective filter 3 a is shown. As shown in FIG. 9, in the wavelengthselective filter 3 a, a phase filter pattern 6 a having concentriccircle shapes is formed on a glass substrate 8 a. And multi layereddielectric films 7 a and 7 b are formed on a glass substrate 8 b. Thewavelength selective filter 3 a has a structure in which a surface,where the phase filter pattern 6 a was not formed, of the glasssubstrate 8 a, and a surface, where the multi layered dielectric films 7a and 7 b were not formed, of the glass substrate 8 b, are adhered by anadhesive.

When the effective diameter of the objective lens 4 a, shown as a dottedline in FIGS. 9 (a) and 9 (b), is defined as 2 a, the phase filterpattern 6 a is formed only within a circular region having the diameter2 b, which is smaller than the diameter 2 a of the objective lens 4 a.As shown in FIG. 9 (c), the cross-section of the phase filter pattern 6a has a four level step shape. The height of each step of the phasefilter pattern 6 a is set to be a value so that the phase difference oflight transmitting between a part with a pattern and a part without apattern at each step becomes 2π (equivalent to 0) for the wavelength 405nm. At this time, this phase difference becomes 1.25π (equivalent to−0.75π) for the wavelength 650 nm.

Therefore, the phase filter pattern 6 a does not change the phasedistribution for the light having wavelength of 405 nm, and changes thephase distribution for the light having wavelength of 650 nm. In casethat the wavelength selective filter 3 a is not used, a sphericalaberration, which remains at the time when the light having wavelengthof 650 nm, inputted to the objective lens 4 a as a collimated light, wastransmitted through the substrate having thickness of 0.6 mm, isdecreased, by setting the magnification of the objective lens 4 a to be0.076. The phase filter pattern 6 a is designed to further decrease thedecreased spherical aberration at the magnification being 0.076 of theobjective lens 4 a by the change of the phase distribution for the lighthaving wavelength of 650 nm.

The multi layered dielectric film 7 a is formed at only the regionwithin the circle of the diameter 2 b, and the multi layered dielectricfilm 7 b is formed at only the region outside the circle of the diameter2 b. The multi layered dielectric film 7 a transmits all of the lighthaving wavelength of 405 nm and all of the light having wavelength of650 nm. And the multi layered dielectric film 7 b transmits all of thelight having wavelength of 405 nm and reflects all of the light havingwavelength of 650 nm.

The phase difference between the light transmitting through the multilayered dielectric film 7 a and the light transmitting through the multilayered dielectric film 7 b is adjusted to be integer times the value of2π for the light having wavelength of 405 nm. That is, at the wavelengthselective filter 3 a, the light having wavelength of 405 nm is alltransmitted, and the light having wavelength of 650 nm is alltransmitted within the region of the circle of the diameter 2 b and isall reflected outside the region of the circle of the diameter 2 b.Therefore, when the focal distance of the objective lens 4 a is decidedas “fa”, the effective numerical aperture for the light havingwavelength of 405 nm is given as “a/fa”, and the effective numericalaperture for the fight having wavelength of 650 nm is given as “b/fa”.For example, it is set to be that the “a/fa”=0.7, and the “b/fa”=0.6.

FIG. 10A is a block diagram showing a structure of the optics 1 a shownin FIG. 8. And FIG. 10B is a diagram showing a structure of a photodetector in the optics 1 a shown in FIG. 10A.

As shown in FIG. 10A, a light having wavelength of 405 nm emitted from asemiconductor laser 9 a is collimated at a collimator lone 10 a. Thecollimated light is inputted to a polarizing beam splitter 11 as a Ppolarized fight, and almost 100% of the P polarized light is transmittedthrough the polarizing beam splitter 11, and is converted from alinearly polarized light to a circularly polarized light at aquarter-wave plate 12, and is transmitted to the disk 5 a.

The light reflected from the disk 5 a is converted from the circularlypolarized light to a linearly polarized light whose polarizationdirection is orthogonal for the forward direction, by transmittingthrough the quarter-wave plate 12. The converted light is inputted tothe polarizing beam splitter 11 as an S polarized light and almost 100%of the inputted light is reflected. The reflected light is received at aphoto detector 15 a by transmitting through a cylindrical lens 13 a anda lens 14 a. The photo detector 15 a is disposed in the middle of thetwo focal lines of the cylindrical lens 13 a and the lens 14 a.

As shown in FIG. 10B, at the photo detector 15 a, the light reflectedfrom the disk 5 a forms a light spot 16 a on light receiving sections 17a to 17 d, divided into four parts. When outputs from the lightreceiving sections 17 a to 17 d are defined to be V17 a to V17 drespectively, the focus error signal is calculated by an equation (V17a+V17 d)−(V17 b+V17 c), by the existing astigmatism method. The trackerror signal is calculated by an equation (V17 a+V17 b)−(V17 c+V17 d),by the existing push-pull method. And the RF signal from the disk 5 a iscalculated by an equation V17 a+V17 b+V17 c+V17 d.

FIG. 11A is a diagram showing a structure of the optics 1 b shown inFIG. 8. And FIG. 11B is a diagram showing a structure of a photodetector in the optics 1 b shown in FIG. 11A.

As shown in FIG. 11A, a light having wavelength of 650 nm emitted from asemiconductor laser 9 b is collimated at a collimator lens 10 b. About50% of the collimated light is transmitted through a half mirror 18 a,and the transmitted light is converted from the collimated light to adiverged light, by transmitting through a concave lens 19 a, and istransmitted to the disk 5 b.

The light reflected from the disk 5 b is converted from a convergentlight to a collimated light, by transmitting through the concave lens 19a. About 50% of the collimated light is reflected at the half mirror 18a and the reflected light is received at a photo detector 15 b bytransmitting through a cylindrical lens 13 b and a lens 14 b. The photodetector 15 b is disposed in the middle of the two focal lines of thecylindrical lens 13 b and the lens 14 b.

As shown in FIG. 11B, at the photo detector 15 b, the light reflectedfrom the disk 5 b forms a light spot 16 b on light receiving sections 17e to 17 h, divided into four parts. When outputs from the lightreceiving sections 17 e to 17 h are defined to be V17 e to V17 hrespectively, the focus error signal is calculated by an equation (V17e+V17 h)−(V17 f+V17 g), by the existing astigmatism method. The trackerror signal is obtained by the phase difference between (V17 e+V17 h)and (V17 f+V17 g), by the existing differential phase detection method.And the RF signal from the disk 5 b is calculated by an equation V17e+V17 f+V17 g+V17 h.

FIG. 12 is a table showing the designed result of the phase filterpattern 6 a in the wavelength selective filter 3 a shown in FIG. 8. InFIG. 12, the left row shows the height of a light inputted to theobjective lens divided by the focal distance of the objective lens. Andthe right row shows the number of steps of the phase filter pattern 6 acorresponding to the left row.

FIG. 13 is a graph showing the calculated result of the wavefrontaberration for the light having wavelength of 650 nm at the firstembodiment of the optical head device of the present invention. In FIG.13 (a), a relation between the height of a light inputted to theobjective lens 4 a divided by the focal distance of the objective lens 4a and the wavefront aberration, at the best image position where thestandard deviation of the wavefront aberration becomes minimum, isshown, in a case that the change of the magnification of the objectivelens 4 a was used and the wavelength selective filter 3 a was not used.And in FIG. 13 (b), a relation between the height of a light inputted tothe objective lens 4 a divided by the focal distance of the objectivelens 4 a and the wavefront aberration, at the best image position wherethe standard deviation of the wavefront aberration becomes minimum, isshown, in a case that the change of the magnification of the objectivelens 4 a was used and also the wavelength selective filter 3 a was used.

As shown in FIG. 13 (b), the standard deviation of the wavefrontaberration is decreased to be 0.047π, by using the change of themagnification of the objective lens 4 a and further using the wavelengthselective filter 3 a. This value is lower than 0.07λ that is theallowable value of the standard deviation of the wavefront aberration,known as Marechel's criterion. And as shown in FIG. 12, the number ofregions of concentric circle shapes, of which the phase filter pattern 6a is composed, is as few as 5, therefore the width of each regionbecomes wide. For example, when the focal distance of the objective lens4 a is decided to be 2.57 mm, the width of the most outside regionbecomes about 59.1 μm. Therefore, it is very easy to manufacture such awavelength selective filter having a phase filter pattern whose eachregion is very wide mentioned above in desiring preciseness.

Each of the multi layered dielectric films 7 a and 7 b has a structurein which a high refractive index layer made of such as titanium dioxideand a low refractive index layer made of such as silicon dioxide arelayered alternately.

FIG. 14A is a graph showing a designed result of a wavelength dependencyof the transmittance for the multi layered dielectric films in thewavelength selective filter at the embodiments of the optical headdevice of the present invention. FIG. 14B is a graph showing a designedresult of a wavelength dependency of the phase of transmitted lightthrough the multi layered dielectric films in the wavelength selectivefilter at the embodiments of the optical head device of the presentinvention.

At the first embodiment of the optical head device of the presentinvention, in FIGS. 14A and 14B, the dotted fine shows the designedresult of the multi layered dielectric film 7 a, and the chain lineshows the designed result of the multi layered dielectric film 7 b, inthe wavelength selective filter 3 a shown in FIG. 9. As shown in FIG.14A, it is understandable that the multi layered dielectric film 7 atransmits all of the light having wavelengths of 405 nm and 650 nm. Andalso it is understandable that the multi layered dielectric film 7 btransmits all of the light having wavelength of 405 nm and reflects allof the light having wavelength of 650 nm.

As shown in FIG. 14B, the phases of light transmitted through the multilayered dielectric films 7 a and 7 b are matched with each other for thewavelength of 405 nm. Therefore, it is understandable that the phasedifference between the transmitted fight was adjusted to integer timesthe value of 2π, for the wavelength of 405 nm. When the thickness ofeach layer of the multi layered dielectric film is made to be thicker,the curves of the wavelength dependency of the transmittance shown inFIG. 14A are shifted to the right side, and the curves of the wavelengthdependency of the phase of transmitted light shown in FIG. 14B are alsoshifted to the right side.

And when the thickness of each layer of the multi layered dielectricfilm is made to be thinner, the curves of the wavelength dependency ofthe transmittance shown in FIG. 14A are shifted to the left side, andthe curves of the wavelength dependency of the phase of transmittedlight shown in FIG. 14B are also shifted to the left side.

Therefore, the thickness of each layer of the multi layered dielectricfilm 7 a can be changed within the range where the transmittances at thewavelengths 405 and 650 nm become about 100%, The thickness of eachlayer of the multi layered dielectric film 7 b can be changed within therange where the transmittance at the wavelength 405 nm becomes about100% and the transmittance at the wavelength 650 nm becomes about 0%.And the phases of the transmitted light through the multi layereddielectric films 7 a and 7 b are adjusted to match with each other atthe wavelength of 405 nm.

As mentioned above, in the designing of the multi layered dielectricfilms, at the wavelength of 405 nm, first, the phase of the lighttransmitting through one of the multi layered dielectric films is madeto be a reference, and then the phase of the light transmitting throughthe other of the multi layered dielectric films is adjusted by using thereference. Therefore, this adjustment can be easily realized, if thereis one of the degree of freedom, being the thickness of each layer ofthe multi layered dielectric films.

In this, FIGS. 14A and 14B are used at the explanation of a secondembodiment of the optical head device of the present invention. Andthere is a continuous line both in FIGS. 14A and 14B, this continuousline is explained later at the second embodiment of the optical headdevice of the present invention.

Next, referring to the drawings, the second embodiment of the opticalhead device of the present invention is explained.

FIG. 15 is a block diagram showing a structure at the second embodimentof the optical head device of the present invention. At the secondembodiment, in case that each function at the second embodiment isalmost equal to each function at the first embodiment, the samereference number is used for the function.

In FIG. 15, each of optics 1 a, 1 b, and 1 c provides a semiconductorlaser and a photo detector that receives a fight reflected from one ofdisks. The wavelength of the semiconductor laser in the optics 1 a is405 nm, the wavelength of the semiconductor laser in the optics 1 b is650 nm, and the wavelength of the semiconductor laser in the optics 1 cis 780 nm.

An interference filter 2 f works to transmit a light having wavelengthof 405 nm and reflect a light having wavelength of 650 nm. Aninterference filter 2 g works to transmit lights having wavelengths of405 nm and 650 nm, and reflect a light having wavelength of 780 nm. Alight emitted from the semiconductor laser in the optics 1 a transmitsthe interference filter 2 f, the interference filter 2 g, and awavelength selective filter 3 b. And the transmitted light is inputtedto an objective lens 4 a as a collimated light, and is focused on a disk5 a, whose thickness is 0.1 mm, of a next generation standard.

A light reflected from the disk 5 a transmits the objective lens 4 a,the wavelength selective filter 3 b, the interference filter 2 g, andthe interference filter 2 f in the inverse direction, and the photodetector in the optics 1 a receives the transmitted light.

A light emitted from the semiconductor laser in the optics 1 b isreflected at the interference filter 2 f and is transmitted through theinterference filter 2 g and the wavelength selective filter 3 b. And thetransmitted light is inputted to the objective lens 4 a as a divergedlight; and is focused on a disk 5 b, whose thickness is 0.6 mm, of theDVD standard. A light reflected from the disk 5 b transmits theobjective lens 4 a, the wavelength selective filter 3 b, and theinterference filter 2 g, in the inverse direction, and is reflected atthe interference filter 2 f, and the photo detector in the optics 1 breceives the transmitted light.

A light emitted from the semiconductor laser in the optics 1 c isreflected at the interference filter 2 g and is transmitted through thewavelength selective filter 3 b. And the transmitted light is inputtedto the objective lens 4 a as a diverged light, and is focused on a disk5 c, whose thickness is 1.2 mm, of the CD standard. A fight reflectedfrom the disk 5 c transmits the objective lens 4 a and the wavelengthselective filter 3 b, in the inverse direction, and is reflected at theinterference filter 2 g, and the photo detector in the optics 1 creceives the transmitted light.

The objective lens 4 a has a spherical aberration, which cancels aspherical aberration generated at the time when the light havingwavelength of 405 nm, inputted to the objective lens 4 a as thecollimated light, was transmitted through the disk 5 a having thicknessof 0.1 mm.

The light having wavelength of 405 nm is inputted to the objective lens4 a as the collimated light, therefore, the magnification of theobjective lens 4 a for the light having wavelength of 405 nm is 0.However, at the time when the light having wavelength of 650 nm,inputted to the objective lens 4 a as the collimated light, transmitsthrough the disk 5 b having thickness of 0.6 mm, a spherical aberrationremains. And when the light having wavelength of 650 nm is inputted tothe objective lens 4 a as the diverged light, a new sphericalaberration, corresponding to the change of the magnification of theobjective lens 4 a, is generated, and this new spherical aberrationworks to decrease the remaining spherical aberration. The magnificationof the objective lens 4 a for the light having wavelength of 650 nm isset to be 0.076.

And at the time when the light having wavelength of 780 nm, inputted tothe objective lens 4 a as the collimated light, transmits the disk 5 chaving thickness of 1.2 mm, a spherical aberration remains. And when thelight having wavelength of 780 nm is inputted to the objective lens 4 aas the diverged light, a new spherical aberration, corresponding to thechange of the magnification of the objective lens 4 a, is generated, andthis new spherical aberration works to decrease the remaining sphericalaberration. The magnification of the objective lens 4 a for the lighthaving wavelength of 780 nm is set to be 0.096.

In this, when an angle, between a paraxial ray, which goes from anobject point to a designated height “r” of the objective lens 4 a, andthe optical axis of the objective lens 4 a, is defined as θo, and anangle, between a paraxial ray, which goes from the designated height “r”of the objective lens 4 a to an image point, and the optical axis of theobjective lens 4 a, is defined as θi, the magnification of the objectivelens 4 a is given as tan θo/tan θi.

When the length, from the object point to the principal point of theobject side of the objective lens 4 a, is defined as lo, and the length,from the principal point of the image side of the objective lens 4 a tothe image point, is defined as li, the tan θo=r/lo, and the tan θi=r/li.The light having wavelength of 405 nm is inputted to the objective lens4 a as the collimated light, therefore, the θo=0, and the lo=∞, and themagnification of the objective lens 4 a becomes 0.

The light having wavelength of 650 nm is inputted to the objective lens4 a as the diverged light, therefore, the θo≠0, and the lo is finite. Atthis time, the value of the lo, that is, the position of the objectpoint, is decided so that the magnification of the objective lens 4 abecomes 0.076. The light having wavelength of 780 nm is inputted to theobjective lens 4 a as the diverged light, therefore, the θo≠0, and thelo is finite. At this time, the value of the lo, that is, the positionof the object point, is decided so that the magnification of theobjective lens 4 a becomes 0.096.

FIG. 16 is a diagram showing the wavelength selective filter 8 b shownin FIG. 15. In FIG. 16 (a), the plane view of the wavelength selectivefilter 3 b, looking from the upper side, is shown, in FIG. 16 (b), theplane view of the wavelength selective filter 3 b, looking from thebottom side, is shown, and in FIG. 16 (c), the sectional view of thewavelength selective filter 3 b is shown. As shown in FIG. 16, in thewavelength selective filter 3 b, a phase filter pattern 6 a havingconcentric circle shapes is formed on a glass substrate 8 a. And multilayered dielectric films 7 c, 7 d, and 7 e are formed on a glasssubstrate 8 b. The wavelength selective filter 3 b has a structure inwhich a surface, where the phase filter pattern 6 a was not formed, ofthe glass substrate 8 a, and a surface, where the multi layereddielectric films 7 c, 7 d, and 7 e were not formed, of the glasssubstrate 8 b, axe adhered by an adhesive.

When the effective diameter of the objective lens 4 a, shown as a dottedline in FIGS. 16 (a) and 16 (b), is defined as 2 a, the phase filterpattern 6 a is formed only within a circular region having the diameter2 b, which is smaller than the effective diameter 2 a of the objectivelens 4 a. As shown in FIG. 16 (c), the cross-section of the phase filterpattern 6 a has a four level step shape. The height of each step of thephase filter pattern 6 a is set to be a value so that the phasedifference of light transmitting between a part with a pattern and apart without a pattern at each step becomes 2π (equivalent to 0) for thewavelength 405 nm. At this tame, the phase difference becomes 1.25π(equivalent to −0.75π) for the wavelength 650 nm, and the phasedifference becomes 1.04π (equivalent to −0.96π) for the wavelength 780nm.

Therefore, the phase filter pattern 6 a does not change the phasedistribution for the fight having wavelength of 405 nm, and changes thephase distribution for the light having wavelengths of 650 nm and 780nm. In case that the wavelength selective filter 3 b is net used, aspherical aberration, which remains at the time when the light havingwavelength of 650 nm, inputted to the objective lens 4 a as a collimatedlight, was transmitted through the substrate having thickness of 0.6 mm,is decreased, by setting the magnification of the objective lens 4 a tobe 0.076. The phase filter pattern 6 a is designed to further decreasethe decreased spherical aberration at the magnification being 0.076 ofthe objective lens 4 a by the change of the phase distribution for thelight having wavelength of 650 nm.

The multi layered dielectric film 7 c is formed at only within thecircular region having the diameter 2 c, which is smaller than thediameter 2 b. The multi layered dielectric film 7 d is formed at onlythe region outside the circle of the diameter 2 c and inside the circleof the diameter 2 b. The multi layered dielectric film 7 e is formed atonly the region outside the circle of the diameter 2 b. The multilayered dielectric film 7 c works to transmit all of the light havingwavelengths of 405 nm, 650 nm, and 780 nm. The multi layered dielectricfilm 7 d works to transmit all of the fight having wavelengths of 405 nmand 650 nm, and reflect all of the light having wavelength of 780 nm.And the multi layered dielectric film 7 e works to transmit all of thelight having wavelength of 405 nm, and reflect all of the light havingwavelengths of 650 nm and 780 nm.

The phase difference between the light transmitting through the multilayered dielectric film 7 c and the light transmitting through the multilayered dielectric film 7 d is adjusted to be integer times the value of2π for the light having wavelength of 405 nm. And also the phasedifference between the fight transmitting through the multi layereddielectric film 7 d and the light transmitting through the multi layereddielectric film 7 e is adjusted to be integer times the value of 2π forthe light having wavelength of 405 nm. And the phase difference betweenthe light transmitting through the multi layered dielectric film 7 c andthe light transmitting through the multi layered dielectric film 7 d isadjusted to be integer times the value of 2π for the fight havingwavelength of 650 nm. That is, at the wavelength selective filter 3 b,the light having wavelength of 405 nm is all transmitted, and the lighthaving wavelength of 650 nm is all transmitted within the region of thecircle of the diameter 2 b and is all reflected outside the region ofthe circle of the diameter 2 b. And the light having wavelength of 780nm is all transmitted within the region of the circle of the diameter 2c and is all reflected outside the region of the circle of the diameter2 c.

Therefore, when the focal distance of the objective lens 4 a is decidedas “fa”, the effective numerical aperture for the light havingwavelength of 405 nm is given as “a/fa”, the effective numericalaperture for the light having wavelength of 650 nm is given as “b/fa”,and the effective numerical aperture for the light having wavelength of780 nm is given as “c/fa”. For example, it is set to be that the“a/fa”=0.7, the “b/fa”=0.6, and the “c/fa”=0.45.

The structure of the optics 1 a is shown in FIG. 10A, and the structureof the photo detector in the optics 1 a is shown in FIG. 10B. And thestructure of the optics 1 b is shown in FIG. 11A, and the structure ofthe photo detector in the optics 1 b is shown in FIG. 11B. That is, theoptics 1 a and 1 b, used at the optical head device of the firstembodiment, are also used at the second embodiment.

FIG. 17A is a block diagram showing a structure of the optics 1 c shownin FIG. 15. And FIG. 17B is a diagram showing a structure of a photodetector in the optics 1 c shown in FIG. 17A.

As shown in FIG. 17A, a light having wavelength of 780 nm emitted from asemiconductor laser 9 c is divided into three lights being 0 th orderlight and ± first order diffracted lights at a diffractive opticalelement 20. The three divided lights become three collimated lights at acollimator lens 10 c. About 50% of the three collimated lights istransmitted through a half mirror 18 b, and is converted into threediverged lights by transmitting through a concave lens 19 b, and istransmitted to the disk 5 c. Three lights reflected from the disk 5 care converted from three convergent lights into three collimated lightsby transmitting through the concave lens 19 b, and about 50% of thecollimated lights is reflected at the half mirror 18 b. The reflectedlights are transmitted through a cylindrical lens 13 c and a lens 14 c,and a photo detector 15 c receives the transmitted lights. The photodetector 15 c is disposed in the middle of the two focal lines of thecylindrical lens 13 c and the lens 14 c.

As shown in FIG. 17B, at the photo detector 15 c, the 0 th order lightfrom the diffractive optical element 20 in the three reflected lightsfrom the disk 5 c forms a light spot 16 c on light receiving sections 17i to 17 l, divided into four parts. The + first order diffracted lightfrom the diffractive optical element 20 forms a light spot 16 d on alight receiving section 17 m. The − first order diffracted fight fromthe diffractive optical element 20 forms a light spot 16 e on a lightreceiving section 17 n.

When outputs from the light receiving sections 17 i to 17 n are definedto be V17 i to V17 n respectively, the focus error signal is calculatedby an equation (V17 i+V17 l)−(V17 j+V17 k), by the existing astigmatismmethod. The track error signal is calculated by an equation V17 m−V17 n,by an existing three beam method. And the RF signal from the disk 5 c iscalculated by an equation V17 i+V17 j+V17 k+V17 l.

The designed result of the phase filter pattern 6 a in the wavelengthselective filter 3 b is shown in FIG. 12. And the calculated result ofthe wavefront aberration, at the best image position where the standarddeviation of the wavefront aberration becomes minimum for the lighthaving wavelength of 650 nm, is shown in FIG. 13. These are the same atthe first embodiment.

FIG. 18 is a graph showing the calculated result of the wavefrontaberration for the light having wavelength of 780 nm at the secondembodiment of the optical head device of the present invention. In FIG.18 (a), a relation between the height of a light inputted to theobjective lens divided by the focal distance of the objective lens andthe wavefront aberration, at the best image position where the standarddeviation of the wavefront aberration becomes minimum, is shown, in acase that the change of the magnification of the objective lens 4 a wasused but the wavelength selective filter 3 b was not used. And in FIG.18 (b), a relation between the height of a light inputted to theobjective lens divided by the focal distance of the objective lens andthe wavefront aberration, at the best image position where the standarddeviation of the wavefront aberration becomes minimum, is shown, in acase that the change of the magnification of the objective lens 4 a wasused and further the wavelength selective filter 3 b was used.

As shown in FIG. 18 (b), the standard deviation of the wavefrontaberration is decreased to be 0.021λ, by using the change of themagnification of the objective lens 4 a and further using the wavelengthselective filter 3 b. This value is lower than 0.07λ that is theallowable value of the standard deviation of the wavefront aberration,known as Marechel's criterion. And as shown in FIG. 12, the number ofregions of concentric circle shapes, of which the phase filter pattern 6a is composed, is as few as 5, therefore the width of each regionbecomes wide. For example, when the focal distance of the objective lens4 a is decided to be 2.57 mm, the width of the most outside regionbecomes about 59.1 μm. Therefore, it is very easy to manufacture thewavelength selective filter 3 b having the phase filter pattern 6 awhose each region is very wide mentioned above in desiring preciseness.

Each of the multi layered dielectric films 7 c, 7 d, and 7 e has astructure in which a high refractive index layer made of such astitanium dioxide and a low refractive index layer made of such assilicon dioxide are layered alternately. As used at the explanation ofthe first embodiment, by using FIGS. 14A and 14B, the multi layereddielectric films 7 c, 7 d, and 7 e are explained.

At the second embodiment of the optical head device of the presentinvention, in FIGS. 14A and 14B, the continuous fine shows the designedresult of the multi layered dielectric film 7 c, the dotted line showsthe designed result of the multi layered dielectric film 7 d, and thechain line shows the designed result of the multi layered dielectricfilm 7 e, in the wavelength selective filter 3 b shown in FIG. 16.

As shown in FIG. 14A, it is understandable that the multi layereddielectric film 7 c transmits all of the light having wavelengths of 405nm, 650 nm, and 780 nm. And also it is understandable that the multilayered dielectric film 7 d transmits all of the light havingwavelengths of 405 nm and 650 nm, and reflects all of the light havingwavelength of 780 nm. Further it is understandable that the multilayered dielectric film 7 e transmits all of the light having wavelengthof 405 nm, and reflects all of the light having wavelengths of 650 nmand 780 nm.

As shown in FIG. 14B, the phases of light transmitted through the multilayered dielectric films 7 c, 7 d, and 7 e are matched with one anotherfor the wavelength of 405 nm, therefore it is understandable that thephase difference among the transmitted light was adjusted to integertimes the value of 2π. And also the phases of light transmitted throughthe multi layered dielectric films 7 c, and 7 d are matched with eachother for the wavelength of 650 nm. Therefore it is understandable thatthe phase difference between the transmitted light was adjusted tointeger times the value of 2π.

When the thickness of each layer of the multi layered dielectric film ismade to be thicker, the curves of the wavelength dependency of thetransmittance shown in FIG. 14A are shifted to the right side, and thecurves of the wavelength dependency of the phase of transmitted lightshown in FIG. 14B are also shifted to the right side.

And when the thickness of each layer of the multi layered dielectricfilm is made to be thinner, the curves of the wavelength dependency ofthe transmittance shown in FIG. 14A are shifted to the left side, andthe curves of the wavelength dependency of the phase of transmittedlight shown in FIG. 14B are also shifted to the left side.

And when the number of layers of the multi layered dielectric film isincreased, the inclination of the curves of the wavelength dependency ofthe transmittance shown in FIG. 14A and the inclination of the curves ofthe wavelength dependency of the phase of transmitted light shown inFIG. 14B are both become steep. On the contrary, when the number oflayers of the multi layered dielectric film is decreased, theinclination of the curves of the wavelength dependency of thetransmittance shown in FIG. 14A and the inclination of the curves of thewavelength dependency of the phase of transmitted light shown in FIG.14B are both become gentle.

Therefore, the thickness of each layer and the number of layers of themulti layered dielectric film 7 c are made to change within the rangewhere the transmittances at the wavelengths 405, 650 nm, and 780 nmbecome about 100%. The thickness of each layer and the number of layersof the multi layered dielectric film 7 d are made to change within therange where the transmittances at the wavelengths 405 nm and 650 nmbecome about 100% and the transmittance at the wavelength 780 nm becomesabout 0%. The thickness of each layer and the number of layers of themulti layered dielectric film 7 e are made to change within the rangewhere the transmittance at the wavelength 405 nm becomes about 100% andthe transmittances at the wavelengths 650 nm and 780 nm become about 0%.And the phases of the transmitted light through the multi layereddielectric films 7 c, 7 d, and 7 e are adjusted to match with oneanother at the wavelength of 405 nm. And the phases of the transmittedlight through the multi layered dielectric films 7 c, and 7 d areadjusted to match with each other at the wavelength of 650 nm.

As mentioned above, in the designing of the multi layered dielectricfilms, at the wavelength of 405 nm, first, the phase of the lighttransmitting through one of the multi layered dielectric films is madeto be a reference, and then the phases of the light transmitting throughthe remaining two multi layered dielectric films are adjusted by usingthe reference. Therefore, this adjustment can be easily realized, ifthere are two of the degree of freedom, being the thickness of eachlayer and the number of layers of the multi layered dielectric films.And at the wavelength of 650 nm, first, the phase of the lighttransmitting through one of the multi layered dielectric films is madeto be a reference, and then the phase of the light transmitting throughthe remaining one multi layered dielectric film is adjusted by using thereference. Therefore, this adjustment can be easily realized, if thereare one of the degree of freedom, being the thickness of each layer ofthe multi layered dielectric films.

At the first and second embodiments of the optical head device of thepresent invention shown in FIGS. 8 and 15, each of the wavelengthselective filters 3 a and 3 b is driven in the focusing direction andthe tracking direction with the objective lens 4 a by an actuator (notshown). In case that only the objective lens 4 a is driven in thefocusing direction and the tracking direction by the actuator, thecenter of the objective lens 4 a deviates for the center of each of thephase filter pattern 6 a in the wavelength selective filters 3 a and 3 bin the focusing direction and the tracking direction. Consequently, anaberration is generated at a light, which is inputted to the objectivelens 4 a as a diverged light and receives the change of the phasedistribution at the phase filter pattern 6 a. However, each of thewavelength selective filters 3 a and 3 b is driven in the focusingdirection and the tracking direction with the objective lens 4 a,therefore this aberration is not generated.

At the first and second embodiments of the optical head device of thepresent invention, the normal line of each of the wavelength selectivefilters 3 a and 3 b slightly inclines for the optical axis of theobjective lens 4 a. In case that the normal line of each of thewavelength selective filters 3 a and 3 b is parallel to the optical axisof the objective lens 4 a, a stray light reflected at each of thewavelength selective filters 3 a and 3 b is inputted to the photodetectors 15 a and 15 b in the optics 1 a and 1 b at the firstembodiment, and is inputted to the photo detectors 15 a, 15 b, and 15 ein the optics 1 a, 1 b, and 1 c at the second embodiment. And an offsetis generated at the focus error signal and the track error signal bythis stray light. However, in case that the normal line of each of thewavelength selective filters 3 a and 3 b slightly inclines for theoptical axis of the objective lens 4 a, this offset is not generated.

As shown in FIG. 9, in the wavelength selective filter 3 a at the firstembodiment of the optical head device of the present invention, thephase filter pattern 6 a is formed on the glass substrate 8 a, and themulti layered dielectric films 7 a and 7 b are formed on the glasssubstrate 8 b. And as shown in FIG. 16, in the wavelength selectivefilter 3 b at the second embodiment of the optical head device of thepresent invention, the phase filter pattern 6 a is formed on the glasssubstrate 8 a, and the multi layered dielectric films 7 c, 7 d, and 7 eare formed on the glass substrate 8 b. However, at the first and secondembodiments of the optical head device of the present invention, thephase filter pattern 6 a can be formed by being unified with the glasssubstrate 8 a, or by being unified with a plastic substrate by molding.Further, the phase filter pattern 6 a and/or the multi layereddielectric films can be formed on the objective lens 4 a.

Next, referring to the drawings, a third embodiment of the optical headdevice of the present invention is explained.

FIG. 19 is a block diagram showing a structure of the third embodimentof the optical head device of the present invention. At the thirdembodiment, in case that each function at the third embodiment is almostequal to each function at the first embodiment, the same referencenumber is used for the function.

In FIG. 19, each of optics 1 a and 1 d provides a semiconductor laserand a photo detector that receives a light reflected from one of disks.The wavelength of the semiconductor laser in the optics 1 a is 405 nm,and the wavelength of the semiconductor laser in the optics 1 d is 650nm. An interference filter 2 f works to transmit a light havingwavelength of 405 nm and reflect a light having wavelength of 650 nm.

A light emitted from the semiconductor laser in the optics 1 a transmitsthe interference filter 2 f and an aperture controlling element 21 a.And the transmitted light is inputted to an objective lens 4 a as acollimated light, and is focused on a disk 5 a, whose thickness is 0.1mm, of a next generation standard. A light reflected from the disk 5 atransmits the objective lens 4 a, the aperture controlling element 21 a,and the interference filter 2 f in the inverse direction, and the photodetector in the optics 1 a receives the transmitted light.

A light emitted from the semiconductor laser in the optics 1 d isreflected at the interference filter 2 f and is transmitted through theaperture controlling element 21 a. And the transmitted light is inputtedto the objective lens 4 a as a diverged light, and is focused on a disk5 b, whose thickness is 0.6 mm, of the DVD standard. A light reflectedfrom the disk 5 b transmits the objective lens 4 a, the aperturecontrolling element 21 a in the inverse direction, and is reflected atthe interference filter 2 f, and the photo detector in the optics 1 dreceives the transmitted fight. The objective lens 4 a has a sphericalaberration, which cancels a spherical aberration generated at the timewhen the light having wavelength of 405 nm, inputted to the objectivelens 4 a as the collimated light, was transmitted through the disk 5 ahaving thickness of 0.1 mm.

The light having wavelength of 405 nm is inputted to the objective lens4 a as the collimated light, therefore, the magnification of theobjective lens 4 a for the light having wavelength of 405 nm is 0.However, at the time when the light having wavelength of 650 nm,inputted to the objective lens 4 a as the collimated light, transmitsthrough the disk 5 b having thickness of 0.6 mm, a spherical aberrationremains. And when the fight having wavelength of 650 nm is inputted tothe objective lens 4 a as the diverged light, a new sphericalaberration, corresponding to the change of the magnification of theobjective lens 4 a, is generated, and this new spherical aberrationworks to decrease the remaining spherical aberration.

The magnification of the objective lens 4 a for the light havingwavelength of 650 nm is set to be 0.076. In this, when an angle, betweena paraxial ray, which goes from an object point to a designated height“r” of the objective lens 4 a, and the optical axis of the objectivelens 4 a, is defined as θo, and an angle, between a paraxial ray, whichgoes from the designated height “r” of the objective lens 4 a to animage point, and the optical axis of the objective lens 4 a, is definedas θi, the magnification of the objective lens 4 a is given as tanθo/tan θi. And when the length, from the object point to the principalpoint of the object side of the objective lens 4 a, is defined as lo,and the length, from the principal point of the image side of theobjective lens 4 a to the image point, is defined as li, the tanθo=r/lo, and the tan θi=r/li.

The light having wavelength of 405 nm is inputted to the objective lens4 a as the collimated light, therefore, the θo=0, and the lo=∞, and themagnification of the objective lens 4 a becomes 0. The light havingwavelength of 650 nm is inputted to the objective lens 4 a as thediverged light, therefore, the θo≠0, and the lo is finite. At this time,the value of the lo, that is, the position of the object point, isdecided so that the magnification of the objective lens 4 a becomes0.076.

FIG. 20 is a diagram showing the aperture controlling element 21 a shownin FIG. 19. In FIG. 20 (a), the plane view of the aperture controllingelement 21 a is shown, and in FIG. 20 (b), the sectional view of theaperture controlling element 21 a is shown. As shown in FIG. 20, theaperture controlling element 21 a has a structure in which multi layereddielectric films 7 a and 7 b are formed on a glass substrate 8 b. Whenthe effective diameter of the objective lens 4 a, shown as a dotted finein FIG. 20 (a), is defined as 2 a, the multi layered dielectric film 7 ais formed only the region within the circle of the diameter 2 b, whichis smaller than the diameter 2 a of the objective lens 4 a. And themulti layered dielectric film 7 b is formed at only outside the circleof the diameter 2 b.

The multi layered dielectric film 7 a transmits all of the light havingwavelength of 405 nm and all of the light having wavelength of 650 nm.And the multi layered dielectric film 7 b transmits all of the lighthaving wavelength of 405 nm and reflects all of the light havingwavelength of 650 nm. And the phase difference between the lighttransmitting through the multi layered dielectric film 7 a and the lighttransmitting through the multi layered dielectric film 7 b is adjustedto be integer times the value of 2π for the light having wavelength of405 nm. That is, at the aperture controlling element 21 a, the lighthaving wavelength of 405 nm is all transmitted, and the light havingwavelength of 650 nm is all transmitted within the region of the circleof the diameter 2 b and is all reflected outside the region of thecircle of the diameter 2 b. Therefore, when the focal distance of theobjective lens 4 a is decided as “fa”, the effective numerical aperturefor the light having wavelength of 405 nm is given as “a/fa”, and theeffective numerical aperture for the light having wavelength of 650 nmis given as “b/fa”. For example, it is set to be that the “a/fa”=0.7,and the “b/fa”=0.6.

In this, the structure of the optics 1 a is the same that used at thefirst embodiment shown in FIG. 10A, and the photo detector 15 a in theoptics 1 a is also the same that used at the first embodiment shown inFIG. 10B.

FIG. 21 is a diagram showing a structure of the optics 1 d shown in FIG.19. As shown in FIG. 21, a light having wavelength of 650 nm emittedfrom a semiconductor laser 9 b is collimated at a collimator lens 10 b.About 50% of the collimated fight is transmitted through a half mirror18 a, and the transmitted fight is converted from the collimated fightto a diverged light, by transmitting through a spherical aberrationcorrecting element 22 a and a concave lens 19 a, and is transmitted tothe disk 5 b. The light reflected from the disk 5 b is converted from aconvergent light to a collimated light, by transmitting through theconcave lens 19 a and the spherical aberration correcting element 22 a.About 50% of the collimated light is reflected at the half mirror 18 aand the reflected light is received at a photo detector 15 b bytransmitting through a cylindrical lens 13 b and a lens 14 b. The photodetector 15 b is disposed in the middle of the two focal lines of thecylindrical lens 13 b and the lens 14 b. The photo detector 15 b in theoptics 1 d is the same that used at the first embodiment shown in FIG.11B.

One of the surfaces of the spherical aberration correcting element 22 ais a plane, and the other of the surfaces is an aspherical surface. Thespherical aberration correcting element 22 a changes the phasedistribution for the light having wavelength of 650 nm. In case that thespherical aberration correcting element 22 a is not used, a sphericalaberration, which remains when the light having wavelength of 650 nm,inputted to the objective lens 4 a as a collimated light, is transmittedthrough the disk 5 b, whose thickness is 0.6 mm, is decreased, by thatthe magnification of the objective lens 4 a is set to be 0.076. Thespherical aberration correcting element 22 a is designed so that thechange of the phase distribution for the light having wavelength of 650nm corrects this decreased spherical aberration at the magnification0.076 of the objective lens 4 a almost completely. In this, thespherical aberration correcting element 22 a can be unified with theconcave lens 19 a.

Each of the multi layered dielectric films 7 a and 7 b in the aperturecontrolling element 21 a has a structure in which a high refractiveindex layer made of such as titanium dioxide and a low refractive indexlayer made of such as silicon dioxide are layered alternately. Thedesigned result of the wavelength dependency of the transmittance foreach of the multi layered dielectric films 7 a and 7 b in the aperturecontrolling element 21 a is the same that shown in FIG. 14A in thewavelength selective filter at the embodiments of the optical headdevice of the present invention. And the designed result of thewavelength dependency of the phase of transmitted light through each ofthe multi layered dielectric films 7 a and 7 b in the aperturecontrolling element 21 a is the same that shown in FIG. 14B in thewavelength selective filter at the embodiments of the optical headdevice of the present invention.

Next, referring to the drawings, a fourth embodiment of the optical headdevice of the present invention is explained.

FIG. 22 is a block diagram showing a structure of the fourth embodimentof the optical head device of the present invention. At the fourthembodiment, in case that each function at the fourth embodiment isalmost equal to each function at the second embodiment, the samereference number is used for the function.

In FIG. 22, each of optics 1 a, 1 d, and 1 e provides a semiconductorlaser and a photo detector that receives a light reflected from one ofdisks. The wavelength of the semiconductor laser in the optics 1 a is405 nm, the wavelength of the semiconductor laser in the optics 1 d is650 nm, and the wavelength of the semiconductor laser in the optics 1 eis 780 nm. An interference filter 2 f works to transmit a light havingwavelength of 405 nm and reflect a light having wavelength of 650 nm. Aninterference filter 2 g works to transmit light having wavelengths of405 nm and 650 nm, and reflect a light having wavelength of 780 nm.

A light emitted from the semiconductor laser in the optics 1 a transmitsthe interference filter 2 f, the interference filter 2 g, and anaperture controlling element 21 b. And the transmitted fight is inputtedto an objective lens 4 a as a collimated light, and is focused on a disk6 a, whose thickness is 0.1 mm, of a next generation standard. A lightreflected from the disk 5 a transmits the objective lens 4 a, theaperture controlling element 21 b, the interference filter 2 g, and theinterference filter 2 f in the inverse direction, and the photo detectorin the optics 1 a receives the transmitted light.

A light emitted from the semiconductor laser in the optics 1 d isreflected at the interference filter 2 f and is transmitted through theinterference filter 2 g and the aperture controlling element 21 b. Andthe transmitted light is inputted to the objective lens 4 a as adiverged light, and is focused on a disk 5 b, whose thickness is 0.6 mm,of the DVD standard. A light reflected from the disk 5 b transmits theobjective lens 4 a, the aperture controlling element 21 b, and theinterference filter 2 g, in the inverse direction, and is reflected atthe interference filter 2 f, and the photo detector in the optics 1 dreceives the transmitted light.

A light emitted from the semiconductor laser in the optics 1 e isreflected at the interference filter 2 g and is transmitted through theaperture controlling element 21 b. And the transmitted light is inputtedto the objective lens 4 a as a diverged light, and is focused on a disk5 c, whose thickness is 1.2 mm, of the CD standard. A light reflectedfrom the disk 5 c transmits the objective lens 4 a and the aperturecontrolling element 21 b, in the inverse direction, and is reflected atthe interference filter 2 g, and the photo detector in the optics 1 ereceives the transmitted light. The objective lens 4 a has a sphericalaberration, which cancels a spherical aberration generated at the timewhen the light having wavelength of 405 nm, inputted to the objectivelens 4 a as the collimated light, was transmitted through the disk 5 ahaving thickness of 0.1 mm.

The light having wavelength of 405 nm is inputted to the objective lens4 a as the collimated light, therefore, the magnification of theobjective lens 4 a for the light having wavelength of 405 nm is 0.However, at the time when the light having wavelength of 650 nm,inputted to the objective lens 4 a as the collimated light, transmitsthrough the disk 5 b having thickness of 0.6 mm, a spherical aberrationremains. And when the light having wavelength of 650 nm is inputted tothe objective lens 4 a as the diverged light, a new sphericalaberration, corresponding to the change of the magnification of theobjective lens 4 a, is generated, and this new spherical aberrationworks to decrease the remaining spherical aberration. The magnificationof the objective lens 4 a for the light having wavelength of 650 nm isset to be 0.076.

And at the time when the light having wavelength of 780 nm, inputted tothe objective lens 4 a as the collimated light, transmits through thedisk 5 c having thickness of 1.2 mm, a spherical aberration remains. Andwhen the light having wavelength of 780 nm is inputted to the objectivelens 4 a as the diverged light, a new spherical aberration,corresponding to the change of the magnification of the objective lens 4a, is generated, and this new spherical aberration works to decrease theremaining spherical aberration. The magnification of the objective lens4 a for the light having wavelength of 780 nm is set to be 0.096.

In this, when an angle, between a paraxial ray, which goes from anobject point to a designated height “r” of the objective lens 4 a, andthe optical axis of the objective lens 4 a, is defined as θo, and anangle, between a paraxial ray, which goes from the designated height “r”of the objective lens 4 a to an image point, and the optical axis of theobjective lens 4 a, is defined as θi, the magnification of the objectivelens 4 a is given as tan θo/tan θi. And when the length, from the objectpoint to the principal point of the object side of the objective lens 4a, is defined as lo, and the length, from the principal point of theimage side of the objective lens 4 a to the image point, is defined asli, the tan θo=r/lo, and the tan θi=r/li. The light having wavelength of405 nm is inputted to the objective lens 4 a as the collimated light,therefore, the θo=0, and the lo=∞, and the magnification of theobjective lens 4 a becomes 0.

The light having wavelength of 650 nm is inputted to the objective lens4 a as the diverged light, therefore, the θo≠0, and the lo is finite. Atthis time, the value of the lo, that is, the position of the objectpoint, is decided so that the magnification of the objective lens 4 abecomes 0.076. The light having wavelength of 780 nm is inputted to theobjective lens 4 a as the diverged light; therefore, the θo≠0, and theis finite. At this time, the value of the lo, that is, the position ofthe object point, is decided so that the magnification of the objectivelens 4 a becomes 0.096.

FIG. 23 is a diagram showing the aperture controlling element 21 b shownin FIG. 22. In FIG. 23 (a), the plane view of the aperture controllingelement 21 b is shown, in FIG. 23 (b), the sectional view of theaperture controlling element 21 b is shown. As shown in FIG. 23, theaperture controlling element 21 b has a structure in which multi layereddielectric films 7 c, 7 d, and 7 e are formed on a glass substrate 8 b.When the effective diameter of the objective lens 4 a, shown as a dottedline in FIG. 23( a), is defined as 2 a, the multi layered dielectricfilm 7 c is formed only within a circular region having the diameter 2c, which is smaller than the diameter 2 b being smaller than theeffective diameter 2 a of the objective lens 4 a. The multi layereddielectric film 7 d is formed at only the region outside the circle ofthe diameter 2 c and inside the circle of the diameter 2 b. The multilayered dielectric film 7 e is formed at only the region outside thecircle of the diameter 2 b.

The multi layered dielectric film 7 c works to transmit all of the lighthaving wavelengths of 405 nm, 650 nm, and 780 nm. The multi layereddielectric film 7 d works to transmit all of the light havingwavelengths of 405 nm and 650 nm, and reflect all of the light havingwavelength of 780 nm. And the multi layered dielectric film 7 e works totransmit all of the light having wavelength of 405 nm, and reflect allof the light having wavelengths of 650 nm and 780 nm. The phasedifference between the light transmitting through the multi layereddielectric film 7 c and the light transmitting through the multi layereddielectric film 7 d is adjusted to be integer times the value of 2π forthe light having wavelength of 405 nm. And also the phase differencebetween the light transmitting through the multi layered dielectric film7 d and the light transmitting through the multi layered dielectric film7 e is adjusted to be integer times the value of 2π for the light havingwavelength of 405 nm. And the phase difference between the lighttransmitting through the multi layered dielectric film 7 c and the lighttransmitting through the multi layered dielectric film 7 d is adjustedto be integer times the value of 2π for the light having wavelength of650 nm.

That is, at the aperture controlling element 21 b, the light havingwavelength of 405 nm is all transmitted, and the light having wavelengthof 650 nm is all transmitted within the region of the circle of thediameter 2 b and is all reflected outside the region of the circle ofthe diameter 2 b. And the light having wavelength of 780 nm is alltransmitted within the region of the circle of the diameter 2 c and isall reflected outside the region of the circle of the diameter 2 c.Therefore, when the focal distance of the objective lens 4 a is decidedas “fa”, the effective numerical aperture for the light havingwavelength of 405 nm is given as “a/fa”, the effective numericalaperture for the light having wavelength of 650 nm is given as “b/fa”,and the effective numerical aperture for the light having wavelength of780 nm is given as “c/fa”. For example, it is set to be that the“a/fa”=0.7, the “b/fa”=0.6, and the “c/fa”=0.45.

In this, the structure of the optics 1 a is the same that used at thefirst embodiment shown in FIG. 10A, and the photo detector 15 a in theoptics 1 a is also the same that used at the first embodiment shown inFIG. 10B. And the optics 1 d is the same that used at the thirdembodiment shown in FIG. 21, and the photo detector 15 b in the optics 1d is the same that used at the first embodiment shown in FIG. 11B.

FIG. 24 is a diagram showing a structure of the optics 1 e shown in FIG.22. As shown in FIG. 24, a light having wavelength of 780 nm emittedfrom a semiconductor laser 9 c is divided into three lights being 0 thorder light and ± first order diffracted lights at a diffractive opticalelement 20. The three divided lights become three collimated lights at acollimator lens 10 c. About 50% of the three collimated lights istransmitted through a half mirror 18 b, and is converted intothree-diverged lights by transmitting through a spherical aberrationcorrecting element 22 b and a concave lens 19 b, and is transmitted tothe disk 5 c. Three lights reflected from the disk 5 c are convertedfrom three convergent lights into three collimated lights bytransmitting through the concave lens 19 b and the spherical aberrationcorrecting element 22 b, and about 50% of the collimated lights isreflected at the half mirror 18 b. The reflected lights are transmittedthrough a cylindrical lens 13 c and a lens 14 c, and a photo detector 15c receives the transmitted lights. The photo detector 15 o is disposedin the middle of the two focal lines of the cylindrical lens 13 c andthe lens 14 c. The structure of the photo detector 15 c is the same thatused at the second embodiment shown in FIG. 17B.

One of the surfaces of the spherical aberration correcting element 22 bis a plane, and the other of the surfaces is an aspherical surface. Thespherical aberration correcting element 22 b changes the phasedistribution for the light having wavelength of 780 nm. In case that thespherical aberration correcting element 22 b is not used, a sphericalaberration, which remains when the light having wavelength of 780 nm,inputted to the objective lens 4 a as a collimated light, is transmittedthrough the disk 5 c, whose thickness is 1.2 mm, is decreased, by thatthe magnification of the objective lens 4 a is set to be 0.096. Thespherical aberration correcting element 22 b is designed so that thechange of the phase distribution for the light having wavelength of 780nm corrects this decreased spherical aberration at the magnification0.096 of the objective lens 4 a almost completely. In this, thespherical aberration correcting element 22 b can be unified with theconcave lens 19 b.

Each of the multi layered dielectric films 7 c, 7 d, and 7 e in theaperture controlling element 21 b has a structure in which a highrefractive index layer made of such as titanium dioxide and a lowrefractive index layer made of such as silicon dioxide are layeredalternately. The designed result of the wavelength dependency of thetransmittance for each of the multi layered dielectric films 7 c, 7 d,and 7 e in the aperture controlling element 21 b is the same that shownin FIG. 14A in the wavelength selective filter at the embodiments of theoptical head device of the present invention. And the designed result ofthe wavelength dependency of the phase of transmitted light through eachof the multi layered dielectric films 7 c, 7 d, and 7 e in the aperturecontrolling element 21 b is the same that shown in FIG. 14B in thewavelength selective filter at the embodiments of the optical headdevice of the present invention.

At the third and fourth embodiments of the optical head device of thepresent invention shown in FIGS. 19 and 22, when the objective lens 4 ais driven in the tracking direction by an actuator (not shown), thecenter of the objective lens 4 a and the center of each of the sphericalaberration correcting elements 22 a and 22 b deviate in the trackingdirection. Consequently, a coma aberration is generated in a lightinputting to the objective lens 4 a as a diverged light, by receiving achange of the phase distribution at each of the spherical aberrationcorrecting elements 22 a and 22 b.

However, this coma aberration can be corrected by that the objectivelens 4 a is inclined in the radial direction of the disks 5 a, 5 b, and5 c by the actuator. When the objective lens 4 a is inclined in theradial direction of the disks 5 a, 5 b, and 5 c, the coma aberration isgenerated. In order to solve the above problem, a coma aberration, whichcancels the coma aberration caused by the deviation of the centers ofthe objective lens 4 a and each of the spherical aberration correctingelements 22 a and 22 b, is generated at the objective lens 4 a byadjusting the incline of the objective lens 4 a in the radial direction.With this, the coma aberration caused by the deviation of the centers ofthe objective lens 4 a and each of the spherical aberration correctingelements 22 a and 22 b is corrected.

Next, referring to the drawings, fifth and sixth embodiments of theoptical head device of the present invention are explained. FIG. 25 is ablock diagram showing a structure of the fifth embodiment of the opticalhead device of the present invention. At the fifth embodiment, relaylenses 23 a and 23 b are added between the interference filter 2 f andthe aperture controlling element 21 a at the third embodiment of theoptical head device of the present invention shown in FIG. 19. And FIG.26 is a block diagram showing a structure of the sixth embodiment of theoptical head device of the present invention. At the sixth embodiment,relay lenses 23 a and 23 b are added between the interference filter 2 gand the aperture controlling element 21 b at the fourth embodiment ofthe optical head device of the present invention shown in FIG. 22.

Generally, when the thickness of the substrate of the disk deviates froma designed value, the shape of the focused light spot is changed by aspherical aberration, caused by the deviation of the thickness of thesubstrate, and the recording and reproducing characteristicsdeteriorate. This spherical aberration is in inverse proportion to thewavelength of the light source, and is in proportion to the fourth powerof the numerical aperture of the objective lens. Therefore, the shorterthe wavelength of the light source is and the higher the numericalaperture of the objective lens is, the narrower the margin for thedeviation of the thickness of the substrate of the disk in the recordingand reproducing characteristics is. In case that the wavelength of thesemiconductor laser 9 a being the light source is 405 nm and thenumerical aperture of the objective lens 4 a is 0.7, this margin is notsufficient, therefore, it is necessary to correct the deviation of thethickness of the substrate of the disk 5 a.

When one of the relay lenses 23 a and 23 b is moved in the optical axisdirection by an actuator (not shown), the magnification of the objectivelens 4 a is changed, and the spherical aberration is changed. Therefore,a spherical aberration, which cancels the spherical aberration caused bythe deviation of the thickness of the substrate of the disk 5 a, isgenerated at the objective lens 4 a by adjusting the position of one ofthe relay lenses 23 a and 23 b in the optical axis direction. With this,the deviation of the thickness of the substrate of the disk 5 a iscorrected and a bad effect for the recording and reproducingcharacteristics becomes almost nothing.

At the fifth and sixth embodiments of the optical head device of thepresent invention shown in FIGS. 25 and 26, when the objective lens 4 ais driven by the actuator in the tracking direction, the center of theobjective lens 4 a deviates in the tracking direction for each of thecenters of the spherical aberration correcting element 22 a in theoptics 1 d and the spherical aberration correcting element 22 b in theoptics 1 e. With this, a coma aberration is generated in a light, whichis inputted to the objective lens 4 a as a diverged light, by receivinga change of the phase distribution at each of the spherical aberrationcorrecting elements 22 a and 22 b.

However, this coma aberration can be corrected by inclining or movingone of the relay lenses 23 a and 23 b in the radial direction of thedisks 5 a, 5 b, and 5 c, by the actuator. In this case, one of the relaylenses 23 a and 23 b is designed not to satisfy the sine condition. Incase that both of the relay lenses 23 a and 23 b satisfy the sinecondition, the coma aberration is not generated, even when the relaylenses 23 a and 23 b are inclined or moved in the radial direction ofthe disks 5 a, 5 b, and 5 c. However, in case that one of the relaylenses 23 a and 23 b does not satisfy the sine condition, the comaaberration is generated, when the relay lenses 23 a and 23 b areinclined or moved in the radial direction of the disks 5 a, 5 b, and 5c.

In order to solve the above problem, by adjusting the incline or theposition of one of the relay lenses 23 a and 23 b in the radialdirection, a coma aberration, which cancels the coma aberration causedby the deviation of the center of the objective lens 4 a for the centerof each of the spherical aberration correcting elements 22 a and 22 b,is generated at one of the relay lenses 23 a and 23 b. With this, thecoma aberration caused by the deviation of the center of the objectivelens 4 a for the center of each of the spherical aberration correctingelements 22 a and 22 b is corrected.

At the third, fourth, fifth, and sixth embodiments of the optical headdevice of the present invention shown in FIGS. 19, 22, 25, and 26, eachof the aperture controlling elements 21 a and 21 b is driven in thetracking direction with the objective lens 4 a by the actuator. In casethat only the objective lens 4 a is driven by the actuator in thetracking direction, the center of the objective lens 4 a deviates in thetracking direction for the center of the multi layered dielectric films7 a and 7 b in the aperture controlling element 21 a or the center ofthe multi layered dielectric films 7 c, 7 d, and 7 b in the aperturecontrolling element 21 b. Consequently, a part of light havingwavelengths of 650 nm and 780 nm, transmitted through the aperturecontrolling element 21 a or 21 b at the forward route, is reflected atthe aperture controlling element 21 a or 21 b at the backward direction.With this, the effective numerical aperture for the light havingwavelengths of 650 nm and 780 nm is lowered.

However, when each of the aperture controlling element 21 a and 21 b andalso the objective lens 4 a are driven in the tracking direction by theactuator, this lowering: of the numerical aperture does not occur.

At the third, fourth, fifth, and sixth embodiments of the optical headdevice of the present invention shown in FIGS. 19, 22, 25, and 26, thenormal line of each of the aperture controlling elements 21 a and 21 bslightly inclines for the optical axis of the objective lens 4 a. Incase that the normal line of each of the aperture controlling elements21 a and 21 b is parallel to the optical axis of the objective lens 4 a,a stray light reflected at each of the aperture controlling elements 21a and 21 b is inputted to each of the photo detectors 15 a, 15 b, and 15c in the optics 1 a, 1 d, and 1 e. And an offset is generated at thefocus error signal and the track error signal by this stray light.However, in case that the normal line of each of the aperturecontrolling elements 21 a and 21 b slightly inclines for the opticalaxis of the objective lens 4 a, this offset is not generated.

As shown in FIG. 20, the aperture controlling element 21 a has astructure in which the multi layered dielectric films 7 a and 7 b areformed on the glass substrate 8 b. And as shown in FIG. 23, the aperturecontrolling element 21 b has a structure in which the multi layereddielectric films 7 c, 7 d, and 7 e are formed on the glass substrate 8b. In this, the multi layered dielectric films can be formed on theobjective lens 4 a.

Next referring to the drawings, embodiments of an optical recording andreproducing apparatus of the present invention are explained.

FIG. 27 is a block diagram showing a structure of a first embodiment ofthe optical recording and reproducing apparatus of the presentinvention. At the first embodiment of the optical recording andreproducing apparatus of the present invention, recording andreproducing circuits 26 a and 26 b, a switching circuit 25 a, and acontrolling circuit 24 a are added to the first embodiment of theoptical head device of the present invention shown in FIG. 8. Therecording and reproducing circuit 26 a generates an input signal to thesemiconductor laser 9 a in the optics 1 a based on a recording signal tothe disk 5 a, and also generates a reproducing signal from the disk 5 abased on an output signal from the pboto detector 15 a in the optics 1a.

The recording and reproducing circuit 26 b generates an input signal tothe semiconductor laser 9 b in the optics 1 b based on a recordingsignal to the disk 5 b, and also generates a reproducing signal from thedisk 5 b based on an output signal from the photo detector 15 b in theoptics 1 b. The switching circuit 25 a switches transmission routes toone of the transmission routes, which are a transmission route of theinput signal to the semiconductor laser 9 a from the recording andreproducing circuit 26 a and a transmission route of the input signal tothe semiconductor laser 9 b from the recording and reproducing circuit26 b. The controlling circuit 24 a controls the operation of theswitching circuit 25 a so that the input signal is transmitted from therecording and reproducing circuit 26 a to the semiconductor laser 9 a incase that the disk 5 a was inserted, and so that the input signal istransmitted from the recording and reproducing circuit 26 b to thesemiconductor laser 9 b in case that the disk 5 b was inserted.

FIG. 28 is a block diagram showing a structure of a second embodiment ofthe optical recording and reproducing apparatus of the presentinvention. At the second embodiment of the optical recording andreproducing apparatus of the present invention, a recording andreproducing circuit 26 c, a switching circuit 25 b, and a controllingcircuit 24 b are added to the first embodiment of the optical headdevice of the present invention shown in FIG. 8. The recording andreproducing circuit 26 c generates an input signal to the semiconductorlaser 9 a in the optics 1 a based on a recording signal to the disk 5 a,and also generates an input signal to the semiconductor laser 9 b in theoptics 1 b based on a recording signal to the disk 5 b. Further, therecording and reproducing circuit 26 c generates a reproducing signalfrom the disk 5 a based on an output signal from the photo detector 15 ain the optics 1 a, and also generates a reproducing signal from the disk5 b based on an output signal from the photo detector 15 b in the optics1 b.

The switching circuit 25 b switches transmission routes to one oftransmission routes, which are a transmission route of the input signalto the semiconductor laser 9 a from the recording and reproducingcircuit 26 c and a transmission route of the input signal to thesemiconductor laser 9 b from the recording and reproducing circuit 26 c.The controlling circuit 24 b controls the operation of the switchingcircuit 25 b so that the input signal is transmitted from the recordingand reproducing circuit 26 c to the semiconductor laser 9 a in case thatthe disk 5 a was inserted, and so that the input signal is transmittedfrom the recording and reproducing circuit 26 c to the semiconductorlaser 9 b in case that the disk 5 b was inserted.

FIG. 29 is a block diagram showing a structure of a third embodiment ofthe optical recording and reproducing apparatus of the presentinvention. At the third embodiment of the optical recording andreproducing apparatus of the present invention, recording andreproducing circuits 26 d, 26 e, and 26 f, a switching circuit 25 c, anda controlling circuit 24 c are added to the second embodiment of theoptical head device of the present invention shown in FIG. 15. Therecording and reproducing circuit 26 d generates an input signal to thesemiconductor laser 9 a in the optics 1 a based on a recording signal tothe disk 5 a, and also generates a reproducing signal from the disk 5 abased on an output signal from the photo detector 15 a in the optics 1a.

The recording and reproducing circuit 26 e generates an input signal tothe semiconductor laser 9 b in the optics 1 b based on a recordingsignal to the disk 5 b, and also generates a reproducing signal from thedisk 5 b based on an output signal from the photo detector 15 b in theoptics 1 b. The recording and reproducing circuit 26 f generates aninput signal to the semiconductor laser 9 c in the optics 1 c based on arecording signal to the disk 5 c, and also generates a reproducingsignal from the disk 5 c based on an output signal from the photodetector 15 c in the optics 1 c.

The switching circuit 25 c switches transmission routes to j one of thetransmission routes, which are a transmission route of the input signalto the semiconductor laser 9 a from the recording and reproducingcircuit 26 d, a transmission route of the input signal to thesemiconductor laser 9 b from the recording and reproducing circuit 26 e,and a transmission route of the input signal to the semiconductor laser9 c from the recording and reproducing circuit 26 f. The controllingcircuit 24 c controls the operation of the switching circuit 25 c sothat the input signal is transmitted from the recording and reproducingcircuit 26 d to the semiconductor laser 9 a in case that the disk 5 awas inserted, and so that the input signal is transmitted from therecording and reproducing circuit 26 e to the semiconductor laser 9 b incase that the disk 5 b was inserted, and so that the input signal istransmitted from the recording and reproducing circuit 26 f to thesemiconductor laser 9 c in case that; the disk 5 c was inserted.

FIG. 30 is a block diagram showing a structure of a fourth embodiment ofthe optical recording and reproducing apparatus of the presentinvention. At the fourth embodiment of the optical recording andreproducing apparatus of the present invention, a recording andreproducing circuit 26 g, a switching circuit 25 d, and a controllingcircuit 24 d are added to the second embodiment of the optical headdevice of the present invention shown in FIG. 15. The recording andreproducing circuit 26 g generates an input signal to the semiconductorlaser 9 a in the optics 1 a based on a recording signal to the disk 5 a,and generates an input signal to the semiconductor laser 9 b in theoptics 1 b based on a recording signal to the disk 5 b, and alsogenerates an input signal to the semiconductor laser 9 c in the optics 1c based on a recording signal to the disk 5 c. Further, the recordingand reproducing circuit 26 g generates a reproducing signal from thedisk 5 a based on an output signal from the photo detector 15 a in theoptics 1 a, and generates a reproducing signal from the disk 6 b basedon an output signal from the photo detector 15 b in the optics 1 b, andalso generates a reproducing signal from the disk 5 c based on an outputsignal from the photo detector 15 c in the optics 1 c.

The switching circuit 25 d switches transmission routes to one of thetransmission routes, which are a transmission route of the input signalto the semiconductor laser 9 a from the recording and reproducingcircuit 26 g, a transmission route of the input signal to thesemiconductor laser 9 b from the recording and reproducing circuit 26 g,and a transmission route of the input signal to the semiconductor laser9 c from the recording and reproducing circuit 26 g. The controllingcircuit 24 d controls the operation of the switching circuit 25 d sothat the input signal is transmitted from the recording and reproducingcircuit 26 to the semiconductor laser 9 a in case that the disk 5 a wasinserted, and so that the input signal is transmitted from the recordingand reproducing circuit 26 g to the semiconductor laser 9 b in case thatthe disk 5 b Was inserted, and so that the input signal is transmittedfrom the recording and reproducing circuit 26 g to the semiconductorlaser 9 c in case that the disk 5 c was inserted.

Further, as embodiments of the optical recording and reproducingapparatus of the present invention, the embodiments, in which arecording and reproducing circuit(s), a controlling circuit, and aswitching circuit are added to each of the optical head devices at thethird, fourth, fifth, and sixth embodiments, can be realized.

As mentioned above, the optical head device of the present inventionprovides a first light source for emitting a light having a firstwavelength, a second light source for emitting a light having a secondwavelength, a photo detector, a wavelength selective filter, anobjective lens. A light emitted from the first light source istransmitted to a first optical recording medium containing a firstsubstrate having a first thickness through the wavelength selectivefilter and the objective lens. And a light emitted from the second lightsource is transmitted to a second optical recording medium containing asecond substrate having a second thickness through the wavelengthselective filter and the objective lens. A light reflected from thefirst optical recording medium is transmitted to the photo detectorthrough the objective lens and the wavelength selective filter. A lightreflected from the second optical recording medium is transmitted to thephoto detector through the objective lens and the wavelength selectivefilter. At the first optical recording medium, information is recordedand the recorded information is reproduced by using the light having thefirst wavelength. At the second optical recording medium, information isrecorded and the recorded information is reproduced by using the lighthaving the second wavelength, And at the optical head device of thepresent invention, the magnification of the objective lens for the lighthaving the first wavelength is different from the magnification of theobjective lens for the light having the second wavelength. Further, thewavelength selective filter changes the phase distribution so that aspherical aberration, which remains for the light having the firstwavelength or the light having the second wavelength at thecorresponding magnification of the objective lens, is decreased.

And as mentioned above, the optical recording and reproducing apparatusof the present invention provides the optical head device of the presentinvention, at least one recording and reproducing circuit, whichgenerates input signals to light sources and also generates reproducingsignals from optical recording media, a switching circuit, whichswitches routes transmitting input signals, and a controlling circuit,which controls the operation of the switching circuit corresponding tothe kinds of the optical recording media.

Consequently, the optical head device and the optical recording andreproducing apparatus of the present invention can realize thecompatibility between the next generation optical recording medium, inwhich the wavelength of the light source is made to be shorter, thenumerical aperture of the objective lens is made to be higher, and thethickness of the substrate of the optical recording medium is made to bethinner, in order to make the recording density higher, and opticalrecording media of conventional DVD standard and CD standard.

The reason, why the above mentioned compatibility is realised, is thatthe remaining spherical aberration is decreased by using the change ofthe magnification of the objective lens for the light having the firstwavelength or the light having the second wavelength, and the decreasedspherical aberration at the corresponding magnification of the objectivelens is further decreased by using the wavelength selective filter.

While the present invention has been described with reference to theparticular illustrative embodiments, it is not to be restricted by thoseembodiments but only by the appended claims. It is to be appreciatedthat those skilled in the art can change or modify the embodimentswithout departing from the scope and spirit of the present invention.

1-88. (canceled)
 89. An optical head device, comprising: a first lightsource for emitting a light having a first wavelength; a second lightsource for emitting a light having a second wavelength; at least onephoto detector; and an objective lens, wherein: an optical system isformed by, a light emitted from said first light source is transmittedto a first optical recording medium through said objective lens, a lightemitted from said second light source is transmitted to a second opticalrecording medium through said objective lens, a light reflected fromsaid first optical recording medium is transmitted to said photodetector through said objective lens, and a light reflected from saidsecond optical recording medium is transmitted to said photo detectorthrough said objective lens, wherein: recording or reproducinginformation is executed for said first optical recording medium by usingsaid light having said first wavelength, and recording or reproducinginformation is executed for said second optical recording medium byusing said light having said second wavelength, wherein: furthercomprising: a spherical aberration correcting element disposed in anoptical path between said first light source and said objective lens orbetween said second light source and said objective lens, wherein: saidspherical aberration correcting element corrects a spherical aberrationremaining for said light having said first wavelength or said lighthaving said second wavelength.
 90. An optical head device in accordancewith claim 89, wherein: said first wavelength is 405 nm, and said secondwavelength is 650 nm.
 91. An optical head device in accordance withclaim 89, wherein: a distance between a surface and a reflective layerfor said first optical recording medium is 0.1 mm, and a distancebetween a surface and a reflective layer for said second opticalrecording medium is 0.6 mm.
 92. An optical head device in accordancewith claim 89, wherein: a magnification of said objective lens for saidlight having said first wavelength is different from a magnification ofsaid objective lens for said light having said second wavelength.
 93. Anoptical head device, comprising: a first light source for emitting alight having a first wavelength; a second light source for emitting alight having a second wavelength; a third light source for emitting alight having a third wavelength; at least one photo detector; and anobjective lens, wherein: an optical system is formed by, a light emittedfrom said first light source is transmitted to a first optical recordingmedium through said objective lens, a light emitted from said secondlight source is transmitted to a second optical recording medium throughsaid objective lens, a light emitted from said third light source istransmitted to a third optical recording medium through said objectivelens, a light reflected from said first optical recording medium istransmitted to said photo detector through said objective lens, a lightreflected from said second optical recording medium is transmitted tosaid photo detector through said objective lens, and a light reflectedfrom said third optical recording medium is transmitted to said photodetector through said objective lens, wherein: recording or reproducinginformation is executed for said first optical recording medium by usingsaid light having said first wavelength, recording or reproducinginformation is executed for said second optical recording medium byusing said light having said second wavelength, and recording orreproducing information is executed for said third optical recordingmedium by using said light having said third wavelength, furthercomprising: a spherical aberration correcting element disposed in anoptical path between said first light source and said objective lens,between said second light source and said objective lens or between saidthird light source and said objective lens, wherein: said sphericalaberration correcting element corrects a spherical aberration remainingfor said light having said first wavelength, said light having saidsecond wavelength or said light having said third wavelength.
 94. Anoptical head device in accordance with claim 93, wherein: said firstwavelength is 405 nm, said second wavelength is 650 nm, and said thirdwavelength is 780 nm.
 95. An optical head device in accordance withclaim 93, wherein: a distance between a surface and a reflective layerfor said first optical recording medium is 0.1 mm, a distance between asurface and a reflective layer for said second optical recording mediumis 0.6 mm, and a distance between a surface and a reflective layer forsaid third optical recording medium is 1.2 mm.
 96. An optical headdevice in accordance with claim 93, wherein: a magnification of saidobjective lens for said light having said first wavelength, amagnification of said objective lens for said light having said secondwavelength, and a magnification of said objective lens for said lighthaving said third wavelength are different from each other.
 97. Anoptical recording or reproducing apparatus, comprising: an optical headdevice in accordance with claim 89, and a recording or reproducingcircuit, which generates an input signal to said first light sourcebased on a recording signal to said first optical recording medium andan input signal to said second light source based on a recording signalto said second optical recording medium, or generates a reproducingsignal from said first optical recording medium based on an outputsignal from said photo detector and a reproducing signal from saidsecond optical recording medium based on an output signal from saidphoto detector.
 98. An optical recording or reproducing apparatus,comprising: an optical head device in accordance with claim 93, and arecording or reproducing circuit, which generates an input signal tosaid first light source based on a recording signal to said firstoptical recording medium, an input signal to said second light sourcebased on a recording signal to said second optical recording medium andan input signal to said third light source based on a recording signalto said third optical recording medium, or generates a reproducingsignal from said first optical recording medium based on an outputsignal from said photo detector, a reproducing signal from said secondoptical recording medium based on an output signal from said photodetector and a reproducing signal from said third optical recordingmedium based on an output signal from said photo detector.